Question 1

A 7-year-old Vietnamese boy is brought to the clinic for a routine health maintenance examination.  He underwent a splenectomy a year ago for persistent anemia and jaundice.  He has received the pneumococcal and meningococcal vaccinations and takes penicillin prophylaxis.  His paternal uncle died from complications of hemolytic uremic syndrome 35 years ago.  Physical examination reveals a well-appearing child.  The sclerae are anicteric.  The abdomen is soft and nontender; no masses are palpable.  Several well-healed laparoscopy scars are noted.  Complete blood count is as follows:  Peripheral blood smear with Wright stain is shown in the exhibit.  This patient's findings are most likely related to which of the following?

Accepted Answer

11ec25c8_d6ad_bdc0_bc81_8da612d94313_MD0003_00 This patient has single, round, blue inclusions within red blood cells (RBCs) on peripheral smear, consistent with Howell-Jolly bodies. These bodies are retained RBC nuclear remnants that are typically removed by the spleen. The presence of Howell-Jolly bodies usually indicates either physical absence of the spleen (ie, asplenia) due to congenital absence or surgical removal or functional hyposplenism due to splenic autoinfarction (eg, sickle cell disease), infiltrative disorders of the spleen (eg, sarcoidosis), or splenic congestion (eg, thrombosis). Both asplenia and functional hyposplenism increase the risk of sepsis because the spleen is normally responsible for clearing bacteria, particularly encapsulated organisms. However, splenectomy may be indicated in cases of chronic hemolysis. (Choice A) In glucose-6-phosphate dehydrogenase deficiency disease, hemoglobin becomes oxidized and precipitates into insoluble Heinz bodies. Peripheral smear shows bite cells, and Heinz bodies appear as peripheral blue inclusions with special staining (eg, crystal violet), not with Wright staining as in this patient. bite cells (Choice B) The inability to produce alpha (alpha thalassemia) or beta (beta thalassemia) globin chains causes hypochromic, microcytic RBCs and target cells (due to decreased hemoglobin production), which can be seen on peripheral smear. target cells (Choice C) Mechanical RBC damage occurs when RBCs shear within the vascular system. This occurs in hemolytic uremic syndrome, disseminated intravascular coagulation, and thrombotic thrombocytopenic purpura. Schistocytes (fragmented RBCs) are seen on peripheral blood smear. Schistocytes (Choice E) Precipitation of ribosomal ribonucleic acid is seen in patients with lead poisoning. In contrast to the single, blue, peripherally-located inclusion characteristic of a Howell-Jolly body, basophilic stippling appears as multiple, scattered, blue granules within the RBC cytoplasm. basophilic stippling Educational objective: Howell-Jolly bodies are nuclear remnants within red blood cells typically removed by the spleen. Their presence strongly suggests asplenia or functional hyposplenism. References: Howell-Jolly bodies: a brief historical review. (http://www.ncbi.nlm.nih.gov/pubmed/21946828)

Question 2

An 8-month-old girl is brought to the clinic by her mother for posthospitalization follow-up.  She was admitted and discharged last week due to fatigue and anemia requiring transfusion of packed red blood cells.  Since going home, the patient has had no issues.  On examination, she is alert and interactive.  Cardiopulmonary examination is unremarkable.  The spleen is palpated 2 cm below the costal margin.  Hemoglobin electrophoresis performed prior to her initial transfusion shows 5% hemoglobin A2 and 95% hemoglobin F.  Her mother asks about the long-term outcome.  It is discussed that the patient will need chronic red blood cell transfusions to maintain her hemoglobin at an appropriate level, but individuals are now able to survive into the fifth and sixth decades of life with supportive management.  In addition to chronic transfusions, the patient will require which of the following supportive medications to improve long-term survival?

Accepted Answer

11ec25c8_d6af_e0a7_bc81_93f4f89133c1_MD0003_00 This patient's hemoglobin electrophoresis results are consistent with beta-thalassemia. Mutations in both beta globin genes result in absent beta globin expression, known as beta-thalassemia major. Instead of the two alpha and two beta chains that typically compose hemoglobin A, patients have increased hemoglobin F (two alpha and two gamma chains) and hemoglobin A2 (two alpha and two delta chains). Since fetal hemoglobin (HbF) predominates in the first few months of life until adult hemoglobin (HbA) is synthesized, beta thalassemia major is generally asymptomatic in the newborn period. Patients around age 6-12 months develop fatigue and pallor due to microcytic anemia. Splenic hemolysis of red blood cells (RBCs) can cause jaundice, dark urine, and splenomegaly. If left untreated, patients can develop skeletal abnormalities due to extramedullary hematopoiesis. synthesized Beta-thalassemia major is transfusion-dependent. The additional iron from transfused RBCs increases the risk for iron overload. Chelation therapy is required to avoid damage to the liver, kidneys, and endocrine glands and improve survival. (Choice B) Hydroxyurea therapy increases HbF in patients with sickle cell disease (by inducing a change in gene expression at the beta globin locus), thereby reducing the relative concentration of hemoglobin S and minimizing complications caused by sickling. (Choice C) Iron supplementation should be avoided in patients with beta-thalassemia as they are at risk for iron overload given their need for transfusions. (Choice D) Penicillin prophylaxis is required for anatomic or functional asplenia due to increased risk of infection with encapsulated organisms. Patients with beta-thalassemia have a functioning spleen. (Choice E) Vitamin B12 deficiency causes macrocytic anemia and is more common in patients with a vegan diet. Educational objective: Beta-thalassemia major is characterized by increased hemoglobin A2 and hemoglobin F on electrophoresis due to absent beta globin expression. Patients are transfusion-dependent and at risk for iron overload. Therefore, chelation therapy is required to improve survival. References: Clinical monitoring and management of complications related to chelation therapy in patients with beta-thalassemia. (http://www.ncbi.nlm.nih.gov/pubmed/26613264)

Question 3

A 1-year-old boy is brought to the clinic to establish care after his family's recent move to the area.  The patient was born at full term and has been growing and developing normally.  Each day, he eats meat and pasta and drinks 300 mL (10 oz) of whole milk; however, he does not eat fruit and vegetables.  The patient takes no daily medications or vitamins.  Weight and height are at the 50th percentile.  Conjunctivae and mucous membranes are pale.  Cardiac examination reveals no murmurs.  Pulmonary examination is normal.  The abdomen is soft, and no hepatosplenomegaly is noted.  Complete blood count results are as follows:  Which of the following is the most likely cause of this patient's anemia?

Accepted Answer

11ec25c8_d6ae_32f2_bc81_79dbf3069b3a_MD0003_00 The most common causes of microcytic anemia in children are iron deficiency and thalassemia. Thalassemia is caused by impaired production of alpha- or beta-globin chains of hemoglobin. Clinical manifestations range from minor to severe, depending on the number of globin chains affected. Alpha- and beta-thalassemia minor (also known as thalassemia trait) are often asymptomatic and found incidentally on laboratory testing. Patients with thalassemia minor are often diagnosed by universal screening for anemia around age 1. Both types of thalassemia minor are characterized by abnormally small red blood cells (RBCs), reflected by a low mean corpuscular volume (MCV). A normal red cell distribution width (RDW) and normal-to-elevated total RBCs typically result in a Mentzer index (MCV/RBC) <13. Reticulocyte count may be slightly elevated due to a compensatory bone marrow response to anemia. Iron studies are typically performed to exclude iron deficiency anemia. Increased RBC turnover in thalassemia minor may result in slightly increased serum iron and ferritin levels. In addition, a peripheral smear of thalassemia shows target and teardrop cells. thalassemia (Choice A) Anemia of chronic disease is typically normocytic and normochromic but can be mildly microcytic; reticulocyte count is low due to decreased erythrocyte production. Anemia of chronic disease is unlikely in this child with no chronic medical problems. (Choice B) Folate deficiency presents as a macrocytic anemia (MCV >100 µm³) and occurs in individuals with poor dietary intake of vegetables or with increased requirements due to chronic hemolysis. macrocytic anemia (Choice C) Hereditary spherocytosis is caused by RBC membrane instability and typically presents with anemia, jaundice, and splenomegaly. Laboratory results demonstrate reticulocytosis, an elevated mean corpuscular hemoglobin concentration, a normal or slightly low MCV, a normal-to-elevated RDW, and spherocytosis. spherocytosis (Choice D) Iron deficiency anemia is the most common cause of microcytic anemia in children and is often caused by excessive cow's milk intake (>700 mL [24 oz] daily). Distinguishing laboratory findings include an increased RDW, a Mentzer index >13 (due to a decline in RBC count), and a low reticulocyte count. Educational objective: Thalassemia minor typically presents with microcytic anemia and a normal red cell distribution width. An elevated reticulocyte count reflects a compensatory bone marrow response to the anemia. References: Thalassaemia. (http://www.ncbi.nlm.nih.gov/pubmed/28774421)

Question 4

A 3-day-old boy is brought to the emergency department due to bruising.  The patient was born at 39 weeks gestation via vaginal delivery at home, and this is his first medical evaluation.  He is breastfed exclusively.  Vital signs are within normal limits.  Several ecchymoses are visible on the extremities.  Physical examination is otherwise unremarkable.  Laboratory results are as follows:  Which of the following is the most likely cause of this patient's condition?

Accepted Answer

11ec25c8_d6b0_55d9_bc81_d947c1729ab0_MD0003_00 This neonate who has not received prior medical care has bruising and prolonged PT and PTT, findings concerning for vitamin K-deficient bleeding (VKDB). Vitamin K is essential for enzymatic carboxylation and activation of coagulation factors II (prothrombin), VII, IX, and X. Newborns are vitamin K deficient due to poor placental transfer, lack of intestinal flora to synthesize vitamin K, and immature liver function (ie, poor vitamin K utilization). Therefore, intramuscular vitamin K is given at birth to prevent spontaneous bleeding. Neonates who do not receive this injection, such as this patient, are at highest risk of VKDB, particularly if exclusively breastfed because breast milk contains insufficient vitamin K. Classic VKDB presents on day 2-7 of life with easy bruising, mucosal bleeding (eg, epistaxis), gastrointestinal hemorrhage, and/or intracranial hemorrhage. Late-onset disease can occur up to age 6 months. Because of reduced coagulation factor carboxylation, laboratory evaluation shows prolonged PT and, in severe deficiency, prolonged PTT. The diagnosis is confirmed by the reversal of laboratory abnormalities with vitamin K administration. (Choice A) Afibrinogenemia is a rare, autosomal recessive bleeding disorder characterized by absent fibrinogen production. Severe bleeding classically develops at the site of the umbilical cord after birth. Like PT and PTT, thrombin time is prolonged. (Choice B) Disseminated intravascular coagulation typically presents with bleeding (eg, bruising, intravenous site oozing) due to consumption of platelets and clotting factors. Laboratory findings include prolonged PT and PTT and thrombocytopenia. This patient's platelet count is normal. (Choices C and D) Severe von Willebrand disease (characterized by impaired synthesis of von Willebrand factor) and factor VIII deficiency (hemophilia A) can present with easy bruising and bleeding in the neonatal period. Both conditions have a prolonged PTT but normal PT. (Choice E) Impaired platelet function can be caused by medications (eg, aspirin), metabolic conditions (eg, uremia, liver disease), or congenital disorders (eg, Glanzmann thrombasthenia). Patients have mucocutaneous bleeding and petechiae; PT, PTT, and platelet count are normal. Educational objective: Vitamin K-deficient bleeding classically presents with bleeding in newborns (day 2-7 of life) who did not receive intramuscular vitamin K, which is essential in the enzymatic carboxylation and activation of coagulation factors II (prothrombin), VII, IX, and X. Symptoms include easy bruising, mucosal bleeding, gastrointestinal bleeding, and/or intracranial hemorrhage; laboratory evaluation reveals prolonged PT with or without prolonged PTT. References: Prevention of vitamin K deficiency bleeding in newborn infants: a position paper by the ESPGHAN committee on nutrition. (http://www.ncbi.nlm.nih.gov/pubmed/27050049) Vitamin K prophylaxis for prevention of vitamin K deficiency bleeding: a systemic review. (http://www.ncbi.nlm.nih.gov/pubmed/27109090)

Question 5

A 5-year-old girl is brought to the clinic due to abdominal cramping and diarrhea.  The diarrhea started 3 days ago and was initially watery but now contains visible mucus.  The patient attends a small day care where several other children have recently developed similar diarrhea.  Temperature is 38.3 C (101 F), blood pressure is 100/62 mm Hg, and pulse is 98/min.  On examination, she appears uncomfortable but is appropriately answering questions and is interactive.  The mouth is slightly dry.  Heart and lung examinations are normal.  The abdomen is diffusely tender to palpation without hepatosplenomegaly.  A stool sample is positive for occult blood, and a stool culture is also obtained.  The patient tolerates fluids she receives in the office.  In addition to encouraging increased fluid intake, which of the following is the most appropriate management of this patient?

Accepted Answer

11ec25c8_d6b2_c6dd_bc81_81322560cafc_MD0003_00 This patient with fever, abdominal cramping, and diarrhea has acute gastroenteritis. Although acute gastroenteritis is most commonly caused by viruses, bacterial infection (eg, Salmonella, Escherichia coli) should be suspected when the stool contains mucus and blood. Stool culture is diagnostic of bacterial gastroenteritis. Well-appearing children with acute diarrhea (as in this case) are treated with supportive care (eg, oral rehydration, antipyretics) and close follow-up only. Antibiotics are not recommended for mild disease (eg, mild dehydration, normal mentation) because their benefit is limited, and antibiotic resistance can occur with unnecessary use (Choice C). In addition, empiric antibiotics increase the risk of life-threatening hemolytic uremic syndrome in patients with bloody diarrhea due to Escherichia coli O157:H7. Patients who are severely ill (eg, extraintestinal disease, worsening/prolonged symptoms, hospitalized) with bacterial gastroenteritis may require antibiotic therapy based on the results of the stool culture. For example, antibiotics may shorten the duration of illness in patients hospitalized for severe Salmonella gastroenteritis that causes high fever and profuse diarrhea. (Choices A and B) Abdominal ultrasound and air contrast enema are used to diagnose and treat intussusception, which presents in young children (age 6 months to 3 years) with episodic abdominal pain and bloody ("currant jelly") stools. In contrast to this patient's persistent cramping and diffuse tenderness, children with intussusception typically have no or only focal abdominal tenderness between painful episodes. In addition, this patient's history of sick contacts makes an infectious cause more likely. (Choice D) Bismuth subsalicylate is not generally recommended in children due to limited benefit and the risk of Reye syndrome and salicylate toxicity. (Choice F) Loperamide is an antimotility drug not recommended in children due to its potential side effects, including paralytic ileus, toxic megacolon, and CNS depression. Also, decreased intestinal motility can prolong fecal shedding of some bacterial diarrheas (eg, Shigella, E coli). Educational objective: Bacterial gastroenteritis should be suspected in a patient with fever, abdominal cramping, and bloody or mucoid diarrhea. Positive stool culture is diagnostic, and treatment is generally supportive care and close follow-up in well-appearing children. Empiric antibiotics are not recommended due to the increased risk of hemolytic uremic syndrome associated with Escherichia coli O157:H7. References: Acute diarrhea in children. (http://www.ncbi.nlm.nih.gov/pubmed/26946776)

Question 6

A newborn boy is evaluated in the nursery an hour after delivery.  The infant was born via vaginal delivery to a 20-year-old primigravid mother who had routine prenatal care.  The pregnancy was complicated by mild gestational hypertension without preeclampsia.  The mother developed a fever 2 days ago and a vesicular rash on her face yesterday.  On the day of delivery, the rash spread to her chest and abdomen and became intensely pruritic.  She went into labor later that day and delivered the infant without difficulty.  Skin-to-skin contact between the mother and infant was deferred due to the maternal rash.  Apgar scores were 8 and 9 at 1 and 5 minutes, respectively.  The boy weighs 2.95 kg (6 lb 8 oz).  Vital signs and physical examination are normal.  The mother does not recall having similar symptoms previously, but the father had a similar rash during his childhood.  Which of the following is the most appropriate management of this infant?

Accepted Answer

11ec25c8_d6b5_5ef3_bc81_ebf1be75e1c6_MD0003_00 This mother's fever and pruritic, vesicular rash are consistent with a primary outbreak of varicella-zoster virus (VZV), or chickenpox. VZV is transmitted via aerosolized droplets and is extremely contagious. Therefore, postexposure prophylaxis (PEP) is recommended for exposed individuals who are not immune, including patients who have not received 2 doses of VZV vaccine or who have not had confirmed varicella infection. A single dose of VZV vaccine does not provide sufficient protection to consider a patient immune. For immunocompetent individuals, PEP is limited to immunization with the live VZV vaccine. However, for high-risk patients who cannot receive VZV vaccine, PEP is achieved by administering passive immunization with varicella-zoster immunoglobulin (VZIG). Patients eligible for VZIG include neonates, pregnant women, and immunocompromised patients. VZIG for neonatal PEP is effective if maternal infection developed 5 days before to 2 days after delivery. (Choice A) VZV vaccine is the recommended method of PEP for patients who are eligible for the vaccine. However, VZV vaccine is a live-virus vaccine and is contraindicated for patients age <1 year. (Choice B) Close observation and follow-up is not indicated in this case as >90% of at-risk, exposed individuals develop varicella and neonatal varicella is a severe disease that usually progresses to systemic involvement (eg, meningoencephalitis, hepatitis). Therefore, PEP is indicated for this newborn. (Choice D) Testing this infant for protective antibody (ie, varicella-specific IgG) is not useful. This infant has not had time to make his own IgG, and because IgG takes 2-3 weeks to develop after illness, the mother will not have transferred any varicella-specific IgG to the infant via the placenta. Therefore, this infant lacks protective antibody. (Choice E) Antiviral therapy (eg, acyclovir) would be indicated if the infant develops varicella disease. However, antiviral therapy has not been shown to be effective for PEP; VZV vaccine or VZIG (for patients who cannot receive vaccine) are the recommended agents. (Choice F) Viral testing is used for diagnosis rather than prevention, and effective PEP in this infant is likely to prevent varicella disease. Furthermore, the incubation period for varicella is 2-3 weeks, and viral testing at 24 hours is likely to be negative even in infected infants. Educational objective: Postexposure prophylaxis is indicated for newborns born to mothers with varicella developing 5 days before to 2 days after delivery. Prophylaxis is achieved by administering varicella-specific immunoglobulin to the infants, who are too young to receive live varicella-zoster virus vaccine. References: Perinatal varicella. (http://www.ncbi.nlm.nih.gov/pubmed/23281363) Varicella-zoster virus (chickenpox) infection in pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/21585641)

Question 7

A 5-year-old boy is brought to the clinic for follow-up of abdominal pain and diarrhea.  Four days prior, he was evaluated at the onset of low-grade fever and mucus-filled diarrhea, and a stool culture was obtained.  The parents were instructed to increase the patient's fluid intake and return in a few days.  Since that time, his fevers have resolved, but he continues to have 5-6 episodes of watery, mucus-filled diarrhea daily.  The patient has no chronic medical conditions.  Temperature is 37.2 C (99 F) and blood pressure is 98/50 mm Hg.  Mucous membranes are moist.  Heart and lung examinations are normal.  The abdomen is mildly distended and diffusely tender to deep palpation without hepatosplenomegaly or masses.  Hemoccult testing is negative.  Stool culture reveals a large growth of Campylobacter coli with the following susceptibilities:  Which of the following is the most appropriate treatment for this patient's condition?

Accepted Answer

11ec25c8_d6b3_631f_bc81_3d3f49625822_MD0003_00 Campylobacter infection (typically C jejuni or C coli) is a foodborne gastrointestinal illness most commonly caused by consumption of undercooked poultry. Infection can also spread via contaminated water or contact with an animal (eg, dog, cat) with Campylobacter diarrhea. Symptoms usually develop around 3 days after exposure and include fever, abdominal pain, and profuse, watery, mucus-filled diarrhea, as seen in this patient. Bloody stools may develop and are more commonly seen in children. Nausea and vomiting are also frequently present. Campylobacter gastroenteritis is generally a self-limited illness. Therefore, treatment is with symptomatic care only (eg, rehydration) for patients with mild disease, such as this patient who is afebrile, well hydrated, and has had nonbloody diarrhea for <7 days. (Choices A, B, C, and D) Antibiotic therapy for Campylobacter gastroenteritis is indicated only in patients with severe disease (eg, duration >7 days, bloody stools, high fevers) or underlying risk factors for severe disease (eg, pregnant, immunocompromised), neither of which are seen in this patient. If this patient's infection were severe, amoxicillin would be the best antibiotic choice based on culture sensitivities. Although the bacteria are sensitive to doxycycline, tetracyclines are generally avoided in children age <8 due to the risk of tooth discoloration. In addition, although azithromycin or levofloxacin is usually used for empiric treatment of severe Campylobacter diarrhea, neither antibiotic would be appropriate for this patient with bacteria resistant to fluoroquinolones and intermediate sensitivity to macrolides. Educational objective: Campylobacter gastroenteritis is most commonly caused by undercooked poultry and presents with fever, abdominal pain, and mucus-filled (sometimes bloody) diarrhea. Disease is typically mild and self-limited, requiring symptomatic care only. References: Global epidemiology of Campylobacter infection. (http://www.ncbi.nlm.nih.gov/pubmed/26062576)

Question 8

A 6-month-old girl is brought to the emergency department due to cough, congestion, and increased work of breathing over the past 2 days.  The patient has been very fussy and has a decreased appetite.  For the last week, her parents and 5-year-old brother have had congestion and rhinorrhea without high fevers or myalgias.  Her brother's school has reported many sick children over the past winter.  Temperature is 37.6 C (99.7 F) and respirations are 65/min.  On examination, the patient is fussy and tachypneic with nasal flaring and subcostal retractions.  Lung examination reveals a prolonged expiratory phase with diffuse crackles and end-expiratory wheezing.  Which of the following is the best next step in management of this patient's condition?

Accepted Answer

11ec25c8_d6b4_e9c2_bc81_d359647c6a47_MD0003_00 This patient has cough, congestion, and increased work of breathing due to bronchiolitis, a lower respiratory tract infection that occurs in children age <2. Respiratory syncytial virus (RSV) is the most common cause and is prevalent in the fall and winter. Other common viral pathogens that cause bronchiolitis include rhinovirus, influenza virus, and parainfluenza virus. Initial symptoms include cough, congestion, and rhinorrhea. Fever may or may not be present. After 2-3 days, inflammation affects the bronchioles, causing diffuse wheezing and/or crackles. Patients may develop hypoxemia and signs of respiratory distress (eg, tachypnea, retractions, nasal flaring), which typically peak on day 3-5 of illness before gradually resolving. Bronchiolitis is a clinical diagnosis. Treatment is supportive and includes nasal saline and suctioning. Hospitalization is indicated for patients requiring intravenous fluids or supplemental oxygen. (Choice A) Antibiotics are used to treat bacterial pneumonia, which presents with fever, cough, and focal crackles. This patient is afebrile with diffuse wheezing and crackles, making viral bronchiolitis more likely. (Choices B and D) Glucocorticoids and racemic epinephrine are used in the treatment of croup, an upper airway infection. Presentation includes fever, barky cough, and inspiratory stridor, none of which are seen in this patient. Glucocorticoids are also indicated for asthma exacerbations, which present with wheezing and respiratory distress. However, they are not beneficial in children age <2 with a first episode of viral-induced wheezing, such as this patient. (Choice C) Loop diuretics are indicated for congestive heart failure, which can cause respiratory distress and crackles. However, this previously healthy patient's congestion, rhinorrhea, and sick contacts are more indicative of an infectious etiology. Educational objective: Bronchiolitis is a viral lower respiratory tract infection that presents in children age <2 with cough, congestion, diffuse wheezes/crackles, and respiratory distress. Diagnosis is clinical, and treatment is supportive (eg, nasal saline and suctioning). References: Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis. (http://www.ncbi.nlm.nih.gov/pubmed/25349312)

Question 9

A 13-year-old girl is brought to the clinic by her mother because the girl has been increasingly tired over the last several months.  The patient's family is from Greece, and her mother and maternal uncles have chronic anemia.  Menarche was 1 year ago.  Menses occur regularly each month, lasting 5-6 days with heavy bleeding and passage of clots, requiring her to wake up multiple times each night to change pads.  The patient is a vegetarian but occasionally eats eggs.  Her family lives in a neighborhood that was built in the 1980s.  Vital signs are normal.  The patient appears pale.  The lungs are clear to auscultation.  A soft systolic ejection murmur is heard in the pulmonic area.  S1 and S2 are normal, and diastole is quiet.  The remainder of the physical examination is normal.  Complete blood count shows:  Which of the following is the best next step in evaluation of this patient?

Accepted Answer

11ec25c8_d6ae_a824_bc81_5546be1bcff0_MD0003_00 Iron deficiency and thalassemia are the most common causes of microcytic anemia (mean corpuscular volume <80 µm³). Both present with fatigue and pallor; however, a history of prolonged bleeding (eg, heavy menses) or poor dietary iron intake raises suspicion for iron deficiency anemia (IDA). Distinguishing laboratory findings of IDA include decreased erythrocyte count (inadequate synthesis) and elevated red cell distribution width due to variable iron levels available throughout the day. In addition, IDA may be associated with reactive thrombocytosis (platelets >400,000/mm³) in response to low red blood cell count. This change is due to megakaryocytes and erythrocytes sharing a common progenitor cell. Although thalassemia should be on the differential diagnosis for a patient of Greek ethnicity with a family history concerning for an inherited thalassemia, this patient also has signs of IDA (heavy menses, decreased erythrocytes, thrombocytosis). Therefore, iron studies are the best next step. Correction of IDA is necessary prior to evaluation of thalassemia with hemoglobin electrophoresis because concomitant iron deficiency can lower hemoglobin A2 and mask the diagnosis (Choice B). (Choice A) Bone marrow biopsy should be considered in patients with more than 2 abnormal cell lines (eg, anemia, leukopenia, thrombocytopenia) to evaluate for acute leukemia or aplastic anemia. Because this patient has isolated anemia and related symptoms, bone marrow biopsy is not yet indicated. Iron studies are also a noninvasive first step in contrast to bone marrow biopsy. (Choice D) Lead poisoning can cause microcytic anemia in children with risk factors for lead exposure (eg, housing built before 1978, eating dirt/paint chips). In contrast, this patient's home was built in the 1980s. (Choice E) Vitamin B₁₂ deficiency is a macrocytic anemia more prevalent in patients with a vegan diet. Educational objective: Iron studies are performed prior to hemoglobin electrophoresis in patients with microcytic anemia suspicious for iron deficiency (eg, heavy menses, low erythrocyte count, reactive thrombocytosis) and concomitant thalassemia (eg, Greek origin, family history). References: Coexisting iron deficiency anemia and beta thalassemia trait: effect of iron therapy on red cell parameters and hemoglobin subtypes. (http://www.ncbi.nlm.nih.gov/pubmed/25006473) Clinicohematological study of thrombocytosis. (http://www.ncbi.nlm.nih.gov/pubmed/20532684)

Question 10

A 5-week-old girl is brought to the emergency department for increased fussiness. The infant had been feeding, voiding, and stooling normally since discharge from the nursery but has become increasingly irritable over the past 48 hours with decreased appetite and frequent crying. Temperature is 38.3 C (100.9 F). Mucous membranes are moist. Heart and lung examinations are unremarkable. The abdomen is soft and nondistended. A 5 × 6 cm area of redness and induration is noted along the left cheek and submandibular region; it has greatly expanded over the past hour. Leukocyte count is 22,000 cells/mm³. Blood, urine, and cerebrospinal fluid are collected for culture. The infant is admitted to the pediatrics unit, and broad-spectrum antibiotics are started. After 5 hours, the blood culture grows gram-positive cocci in pairs and chains. Which of the following is the most likely pathogen in this patient?

Accepted Answer

11ec25c8_d6b7_5ac7_bc81_e39cb0821f3e_MD0003_00 This infant with gram-positive cocci in pairs and chains on blood culture most likely has infection due to Streptococcus agalactiae, also known as group B Streptococcus (GBS). GBS is the most common cause of early-onset neonatal sepsis in the first week of life (typically first 24 hours) due to vertical transmission during passage through a colonized vaginal canal. However, GBS can also cause late-onset infection in young infants age ≥7 days due to horizontal transmission of bacteria from colonized household members. Maternal intrapartum antibiotic prophylaxis does not reduce the incidence of late-onset disease. gram-positive cocci in pairs and chains Late-onset GBS most commonly presents at age 4-5 weeks with bacteremia, meningitis, or a focal infection (eg, cellulitis, osteomyelitis). This patient has cellulitis-adenitis, a well-described manifestation of GBS characterized by inflammation and induration of the face and/or submandibular area, often with associated adenopathy. Fever may be present, and patients typically have concomitant bacteremia. Workup includes blood, urine, and cerebrospinal fluid cultures as well as initiation of empiric antibiotics. Growth of S agalactiae on culture, which appears as gram-positive cocci arranged in pairs and short chains, is diagnostic. Definitive treatment is intravenous penicillin G. (Choices A and B) Clostridium perfringens and Corynebacterium species are gram-positive rods that cause gangrenous wound infections and respiratory symptoms (eg, diphtheria), respectively. (Choice C) Enterococcus faecalis is a gram-positive coccus that organizes into pairs and chains similar to GBS; however, E faecalis is a much less common cause of late-onset neonatal infection than GBS, and it typically causes urinary tract infections, not skin infections. (Choice D) Late-onset neonatal listeriosis can present with fever, poor feeding, and bacteremia, but cellulitis does not occur. In addition, Listeria monocytogenes is a gram-positive rod, not a coccus. (Choice E) Staphylococcus aureus infection should be suspected in a patient with cellulitis, but S aureus appears as gram-positive cocci in clusters, not in pairs and chains. Educational objective: Streptococcus agalactiae (group B Streptococcus) are gram-positive cocci in pairs and chains on culture. It can cause early-onset neonatal sepsis or late-onset disease in young infants. Late-onset infection most commonly presents at age 4-5 weeks with bacteremia, meningitis, and/or focal infection (eg, cellulitis-adenitis). References: Management of infants at risk for group B streptococcal disease. (http://www.ncbi.nlm.nih.gov/pubmed/31285392) Group B streptococcal cellulitis and necrotizing fasciitis in infants: a systematic review. (http://www.ncbi.nlm.nih.gov/pubmed/29424798)

Question 11

A 2-year-old boy is brought to the emergency department following a 2-minute, generalized tonic-clonic seizure at home, which resolved spontaneously.  The patient was behaving normally until last night, when he appeared to have abdominal pain and felt "warm to the touch."  He has had no emesis but has been having frequent watery, loose stools over the past day that now contain blood and mucus.  Temperature is 39.7 C (103.5 F), blood pressure is 100/62 mm Hg, pulse is 140/min, and respirations are 26/min.  The patient is awake, active, and responsive.  The pupils are equal and reactive, and the fundi appear normal.  The oral mucosa is dry.  The abdomen is soft with hyperactive bowel sounds and left lower quadrant tenderness to palpation.  There is no hepatosplenomegaly or abdominal masses.  Cranial nerve examination and deep tendon reflexes are normal.  Which of the following is the most likely cause of this patient's symptoms?

Accepted Answer

11ec25c8_d6b2_2a9c_bc81_37f4d72a6331_MD0003_00 This patient has findings concerning for acute bacterial gastroenteritis (eg, fever, abdominal pain, bloody diarrhea), which can be caused by pathogens such as Escherichia coli O157:H7, Shigella, Campylobacter, and Salmonella. In children, seizures in the setting of acute bacterial gastroenteritis should raise concern for Shigella infection. Shigella sonnei is transmitted by ingestion of contaminated food or water and is sometimes implicated in outbreaks in community settings (eg, day care facilities) due to the low infectious dose required for person-to-person spread. Shigella gastroenteritis presents abruptly with high fever, intestinal cramping, and stools that are initially watery before mucus and/or blood appears. Shigella preferentially involves the rectosigmoid region (ie, left lower quadrant), causing frequent, small-volume but bloody/mucoid diarrhea; tenesmus is also common. Seizure is a severe complication that can occur in children with Shigella infection. The seizure may be provoked by fever from the infection (ie, febrile seizure) or caused by enterotoxins produced by the organism itself. Other potential complications of Shigella include rectal prolapse (due to severe rectal inflammation), bacteremia (associated with increased fatality), and hemolytic uremic syndrome (HUS). Diagnosis is confirmed by stool culture, and treatment involves supportive care (eg, rehydration), as well as antibiotic therapy for symptomatic patients. Symptoms typically resolve within a week. In contrast to E coli O157:H7 diarrhea, in shigellosis, antibiotics do not increase the risk of HUS. (Choices A and B) Clostridium perfringens and enterotoxigenic E coli cause watery, nonbloody diarrhea. High-grade fever and associated seizures are unusual with these infections. (Choice C) Intussusception can be a rare complication of viral gastroenteritis. Gastroenteritis symptoms may include watery diarrhea, fever, and seizures if dehydration is severe, whereas telescoping of bowel segments (ie, intussusception) due to hypertrophy of Peyer patches in the terminal ileum can result in episodic abdominal pain and bloody stools. However, ileal involvement causes right, not left, lower quadrant pain. In addition, a sausage-shaped abdominal mass is often palpable but is not present in this patient. Intussusception (Choice E) Ulcerative colitis, which is rare in children age <5, can cause abdominal pain, fever, and bloody diarrhea. However, symptom onset is typically gradual, and seizures are not seen. Educational objective: Gastroenteritis caused by Shigella sonnei presents acutely with high fever, abdominal cramping, and mucoid and/or bloody diarrhea. It may be associated with seizures in children. References: Gastrointestinal and extra-intestinal manifestations of childhood shigellosis in a region where all four species of Shigella are endemic. (http://www.ncbi.nlm.nih.gov/pubmed/23691156) Neurological manifestations of shigellosis in children in southwestern Iran. (http://www.ncbi.nlm.nih.gov/pubmed/22115119)

Question 12

A 4-month-old boy is brought to the clinic by his mother due to concerns of appearing pale.  Over the past few days, he has been sleeping more than usual and is less interactive.  The boy is exclusively breastfed, and he slept through two of his usual feeding sessions yesterday.  He continues to have good urine output.  The patient was born at 40 weeks gestation and had a normal nursery course.  His mother's prenatal course was unremarkable.  However, the patient's newborn screen revealed an extra band representing gamma tetramers on hemoglobin electrophoresis.  The patient takes a vitamin D supplement daily.  Vital signs are normal.  He appears tired and has mild scleral icterus.  The remainder of the examination shows no abnormalities.  Laboratory evaluation of this patient would most likely show which of the following?

Accepted Answer

Explanation: 11ec25c8_d6af_4466_bc81_ffc6deba21b5_MD0003_00 Normal hemoglobin is a heterotetramer composed of 4 chains: Normal hemoglobin 2 alpha and 2 beta chains in children and adults (adult hemoglobin), or 2 alpha and 2 gamma chains in fetuses and infants (fetal hemoglobin) In patients with alpha-thalassemia, ≥1 alpha genes are deleted. When 3 genes are lost (α-/--), a condition known as hemoglobin H disease, the nonalpha chains accumulate into homotetramers; in children and adults, these homotetramers are composed of beta chains (hemoglobin H) whereas, in fetuses and infants, they are composed of gamma chains (hemoglobin Barts), as seen in this patient. Hemoglobin H disease usually presents in infancy with chronic hemolysis due to a shorter red blood cell (RBC) lifespan and increased splenic sequestration. Elevated erythrocyte count and reticulocytosis occur as the bone marrow attempts to replenish hemolyzed RBCs. However, RBCs are microcytic (mean corpuscular volume <80 µm³) and hypochromic because hemoglobin accounts for the majority of RBC volume. Characteristic findings on peripheral smear include abundant target cells as a result of the reduced RBC volume. ³ peripheral smear The presence of gamma tetramers (hemoglobin Barts) on hemoglobin electrophoresis should raise suspicion for alpha-thalassemia; it is classically associated with hydrops fetalis, the most severe form of alpha-thalassemia, which is due to 4 alpha gene loss (--/--) and typically leads to death in utero. (Choice A) Increased destruction of RBCs seen in microangiopathic hemolytic anemia results in a decreased erythrocyte count and schistocytes on peripheral smear. schistocytes (Choice B) Patients with hereditary spherocytosis have a defective RBC membrane protein that results in spherocytes on peripheral smear. Erythrocyte count is decreased due to destruction of spherocytes in the spleen. spherocytes (Choice C) Secondary erythrocytosis is characterized by an increase in immature erythrocytes (polychromasia) in response to hypoxia or tumor. Hemoglobin electrophoresis would not show gamma tetramers. polychromasia (Choice D) Iron deficiency causes a microcytic, hypochromic anemia similar to thalassemia. However, decreased RBC production due to inadequate iron stores results in a low erythrocyte count and pencil cells on peripheral smear. microcytic, hypochromic Educational objective: The presence of gamma tetramers (hemoglobin Barts) on hemoglobin analysis is consistent with alpha-thalassemia. Laboratory studies typically reveal a microcytic anemia, an elevated erythrocyte count, and target cells on peripheral smear. References: Heterogeneity of hemoglobin H disease in childhood. (http://www.ncbi.nlm.nih.gov/pubmed/21345100) Alpha-thalassemia. (http://www.ncbi.nlm.nih.gov/pubmed/20507641)

Question 13

A 14-year-old girl is brought to the emergency department due to 2 days of abdominal cramping, nausea, vomiting, and diarrhea.  Today, she has developed fever and blood in the stool.  The patient recently returned from a week-long summer camp and had no symptoms while she was away.  She has common variable immunodeficiency that is managed with immunoglobulin replacement therapy.  Prior to this illness, the patient had been generally well, except for an episode of sinusitis a month ago that was treated with amoxicillin-clavulanate.  Temperature is 38.2 C (100.8 F) and pulse is 102/min.  Abdominal examination shows mild, diffuse pain with palpation but no rebound tenderness or guarding.  Stool ova and parasite testing is negative.  Stool culture grows Salmonella species.  Which of the following is the most likely underlying cause of this patient's current condition?

Accepted Answer

11ec25c8_d6b1_8e5b_bc81_1dc307aa33ee_MD0003_00 Salmonella subspecies are categorized as nontyphoidal or typhoidal according to the causative strain and clinical manifestations. This patient likely has nontyphoidal Salmonella (eg, S Enteritidis), a common cause of bacterial food-borne illness. Most cases arise from ingestion of undercooked poultry or eggs. Inadequate refrigeration of prepared foods is also a common source because warm temperatures are ideal for Salmonella growth. Symptoms begin within 3 days of ingestion and usually include fever, vomiting, diarrhea, and abdominal pain. Bloody stools are uncommon in adults but may be seen in children. In contrast, typhoidal Salmonella (eg, S Typhi) causes typhoid fever, an invasive, potentially fatal illness characterized by bacteremia and high fever; diarrhea can occur. Typhoidal strains are largely endemic to resource-limited countries with poor sanitation, and fecal-oral transmission occurs via consumption of contaminated food or water. The typhoid vaccine, which is administered to patients prior to travel abroad, protects against typhoidal strains of Salmonella only (Choice E). Although patients with primary humoral immunodeficiency may have a deficient response to immunizations and may be at increased risk for vaccine-preventable diseases even if immunized, this child has symptoms consistent with nontyphoidal Salmonella, for which there is no vaccine. (Choice A) Bacteremia and sepsis can result from an infusion contaminated by gram-negative bacteria, such as Salmonella. However, infusate contamination is very rare, and patients are ill-appearing with high fever and chills. In addition, blood, not stool, culture would be expected to grow bacteria. (Choice B) Antibiotic use can disrupt the normal microbiota of the gastrointestinal tract and is associated with an increased risk of Clostridioides difficile infection. Symptoms include abdominal pain, fever, and diarrhea that is watery at onset. Salmonella infection is not associated with recent antibiotic use. (Choice D) Ingestion of raw or unrefrigerated seafood can lead to diarrhea with or without blood due to Vibrio parahaemolyticus, not Salmonella, gastroenteritis. Educational objective: Nontyphoidal Salmonella is a common cause of bacterial food-borne gastroenteritis, and most cases arise from the ingestion of undercooked poultry or eggs or improperly refrigerated food. Symptoms include fever, abdominal pain, vomiting, and diarrhea with or without blood. References: A review of temperature, pH, and other factors that influence the survival of Salmonella in mayonnaise and other raw egg products. (http://www.ncbi.nlm.nih.gov/pubmed/27869756)

Question 14

A 4-year-old girl is brought to the clinic by her parents due to painful swelling in her groin, which began 2 weeks ago and has gradually become red and tender.  Cool compresses and over-the-counter analgesics have not improved her symptoms.  The patient attends preschool 3 times a week and returned from a family trip to China 2 months ago.  The family has 2 dogs, a cat, and a turtle.  Temperature is 37.4 C (99.3 F); other vital signs are normal.  Examination shows a small, nontender papule on the anterior left thigh.  There is a 4-cm, tender, soft, and freely mobile left inguinal lymph node with overlying erythema.  Which of the following is the most likely causative organism of this patient's condition?

Accepted Answer

11ec25c8_d6b4_7491_bc81_a70b08b12c42_MD0003_00 A localized papule with ipsilateral regional lymphadenopathy in the setting of cat exposure raises concern for cat-scratch disease (CSD). CSD, caused by Bartonella henselae, is a fastidious gram-negative bacillus carried by the majority of cats, especially kittens. B henselae can be transmitted by a cat scratch or bite, or (rarely) by a flea. However, the majority of patients do not recall a specific scratch or bite. Classically, patients present with a localized papular or nodular skin lesion that may initially go unnoticed. Additional presenting symptoms may include fever of unknown origin and/or regional lymphadenopathy in the subsequent 1-2 weeks. Affected lymph nodes are enlarged, tender, and have overlying erythema; suppuration is less common. Lymphadenopathy may take 1-2 months to resolve. Cat exposure and symptoms consistent with CSD are usually sufficient to make a clinical diagnosis. Although many mild cases will self-resolve, treatment with azithromycin is typically recommended. (Choice B) Mycobacterium tuberculosis should be considered in patients with lymphadenopathy (especially cervical) or who have traveled to an endemic region (eg, China). Similar to CSD, the onset may be gradual; however, adenitis due to M tuberculosis is strikingly nontender. (Choice C) Pasteurella multocida, normal oral flora in dogs and cats, can cause cellulitis and other soft tissue infection within 1-2 days of a dog or cat bite. This patient's adenopathy with indolent onset is inconsistent with P multocida. (Choice D) Salmonella enteritidis is carried by reptiles (including turtles) and can cause severe mesenteric adenitis in conjunction with enteritis. Cutaneous lesions are inconsistent with Salmonella infection. (Choices E and F) Staphylococcus aureus and Streptococcus pyogenes are common causes of acute bacterial lymphadenitis, which presents with a warm, tender, erythematous lymph node. However, this child's papular skin lesion and gradual symptom onset are inconsistent with acute bacterial lymphadenitis. Educational objective: Cat-scratch disease, caused by Bartonella henselae, most commonly presents with a mild papular or nodular skin lesion and ipsilateral lymphadenitis of gradual onset. These symptoms in the setting of cat exposure are sufficient to make a clinical diagnosis of cat-scratch disease. References: Cat-scratch disease. (http://www.ncbi.nlm.nih.gov/pubmed/21243990)

Question 15

An 18-month-old boy is brought to the emergency department due to blood in his stool, which the parents noticed when changing his diaper. The infant has had no previous bleeding and has been eating and drinking normally. He has a history of recurrent otitis media, frequent herpes labialis, and 2 episodes of pneumonia. Vital signs are normal. On examination, the patient is well developed, well nourished, and has a fair complexion. He has eczema on his cheeks, trunk, and extremities. Scattered petechiae are also visible on his lower extremities. The remainder of the physical examination is unremarkable. Laboratory studies show a platelet count of 24,000/mm³ and a leukocyte count of 9,000/mm³. Peripheral smear confirms the low platelet count and that the platelets are small. Genetic testing confirms the diagnosis. Which of the following processes is most likely affected by this patient's gene mutation?

Accepted Answer

11ec25c8_d6b0_f21a_bc81_57746451a10b_MD0003_00 This patient's eczema (itchy, red, scaly skin), microthrombocytopenia (small and low number of platelets), and recurrent infections are consistent with Wiskott-Aldrich syndrome (WAS). WAS is caused by an X-linked recessive defect in the WAS gene. This gene is primarily expressed in hematopoietic cells and regulates cytoskeleton remodeling in response to cell signaling. In WAS, the actin cytoskeleton in white blood cells is abnormal, resulting in immune dysfunction due to impaired cellular migration and immune synapse formation. Patients are at increased risk for recurrent bacterial, viral, and fungal infections. Similarly, the cytoskeleton of platelets is also dysfunctional. Virtually all patients have significantly decreased platelet counts and size at the time of diagnosis. The resulting clinical findings can range from petechiae or purpura to severe bleeding such as intracranial hemorrhage, hematemesis, or hematochezia. In addition, autoimmune disorders (eg, eczema) occur in most patients with WAS. The treatment of WAS is hematopoietic stem cell transplantation. (Choice A) T cell lymphocytes that lack CD40 ligand cannot bind to the CD40 receptor on B cells. Without CD40 activation, B cells cannot switch the antibody isotype they produce (eg, from IgM to IgG or IgA), resulting in hyper-IgM syndrome. (Choice C) Ataxia telangiectasia is a T cell deficiency associated with a defect in DNA repair. In addition to immune dysfunction, patients with ataxia telangiectasia experience progressive cerebellar degeneration and are at high risk for cancer. (Choice D) Chronic granulomatous disease results from an inability of phagocytes to produce hydrogen peroxide in their lysosomes. Abscesses due to fungi or catalase-positive bacteria (eg, Staphylococcus aureus) are the characteristic feature. (Choice E) Severe combined immunodeficiency (SCID) results from a severe T cell deficiency. A variety of gene defects can cause SCID and all prevent interleukin-7-driven maturation of T cells in the thymus. Patients with SCID have virtually no functional T cells; lack of T cells causes severe B cell dysfunction as well. Educational objective: Wiskott-Aldrich syndrome is an X-linked disorder characterized by the triad of thrombocytopenia, eczema, and recurrent infections. The thrombocytopenia is the most consistent feature and is characterized by a significant reduction in platelet volume and size. References: Wiskott-Aldrich syndrome: diagnosis, current management, and emerging treatments. (http://www.ncbi.nlm.nih.gov/pubmed/24817816) WASP-WIP complex in the molecular pathogenesis of Wiskott-Aldrich syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/26331277)

Question 16

A 1-day-old boy is admitted to the neonatal intensive care unit due to microcephaly. Microcephaly and ventriculomegaly were first seen during an antenatal sonogram at 20 weeks gestation. Follow-up ultrasounds revealed progressive fetal growth restriction for which a cesarean delivery was performed at 35 weeks gestation. The mother is a 28-year-old woman, gravida 3 para 3, who is healthy and took prenatal vitamins. The infant's 2 siblings, age 18 months and 4 years, are healthy. Weight and length are at the 5th percentile, and head circumference is <3rd percentile. Temperature is 37.2 C (99 F), and the remaining vital signs are normal. Physical examination shows a jaundiced infant who is small for gestational age. The lungs are clear to auscultation, and no murmurs are audible. The liver edge is palpable at the level of the umbilicus. Platelet count is 25,000/mm³. CT scan of the head is shown below. The most likely source of congenital infection is maternal exposure to which of the following?

Accepted Answer

11ec25c8_d6b6_be86_bc81_217e4afbc753_MD0003_00 This infant has microcephaly with periventricular calcifications on CT scan, features suggestive of congenital cytomegalovirus (CMV). CMV infection is common in children age 1-4 (particularly those who attend day care), and pregnant women typically acquire CMV through contact with body fluids (eg, urine, saliva) of infected children. Maternal infection is often asymptomatic but may present as a nonspecific, mild viral illness. CMV is then transmitted vertically from mother to fetus via placental transfer. Early (ie, first trimester) primary maternal infection is associated with higher infant morbidity as compared with recurrent maternal infection or infection late in pregnancy. Although most infected neonates are asymptomatic at birth, microcephaly with periventricular calcifications and ventriculomegaly (as seen in this patient) is highly suspicious for congenital CMV. Other clinical features include intrauterine growth restriction, hepatosplenomegaly, jaundice, and thrombocytopenia. In addition, sensorineural hearing loss is a common sequela that can occur in the presence or absence of other symptoms. Diagnosis is typically confirmed with PCR by detection of CMV in the urine or saliva. periventricular calcifications (Choices A and D) Toxoplasmosis can be transmitted via exposure to cat feces, either directly (eg, kitty litter) or indirectly (eg, unwashed, soil-contaminated fruits and vegetables). Transmission can also occur via consumption of undercooked meat from infected animals. Congenital toxoplasmosis commonly presents with hydrocephalus and diffuse parenchymal calcifications rather than periventricular calcifications. (Choice B) Congenital syphilis results from maternal Treponema pallidum infection, which is most commonly transmitted via sexual contact with a genital lesion of an infected individual. Infants with congenital syphilis can have bone lesions, growth restriction, petechiae, and jaundice but do not have microcephaly or calcifications. (Choice C) Zika virus is transmitted through the bite of an infected mosquito. Congenital infection can cause microcephaly and intracerebral (not periventricular) calcifications. Hepatosplenomegaly is not associated with congenital Zika virus infection. Educational objective: Characteristic features of congenital cytomegalovirus (CMV) infection include microcephaly and periventricular calcifications. Pregnant women most commonly acquire CMV through contact with infected body fluids (eg, saliva) and transmit the infection vertically to the fetus via placental transfer. References: Cytomegalovirus infection. (http://www.ncbi.nlm.nih.gov/pubmed/22474112) Prevention of maternal and congenital cytomegalovirus infection. (http://www.ncbi.nlm.nih.gov/pubmed/22510635)

Question 17

A 6-hour-old boy is being evaluated in the nursery.  He was born at 39 weeks gestation via spontaneous vaginal delivery to a 33-year-old primigravida.  The pregnancy was complicated by intravenous drug use, and the mother was incarcerated for 2 months during the second trimester.  First trimester serologies, including RPR, HIV antibodies, and hepatitis B surface antigen (HBsAg), were negative.  Due to the mother's risk profile, follow-up testing was obtained during the third trimester and revealed the following:  Liver function testing was normal.  Hepatitis C and repeat HIV testing were negative.  The remainder of the pregnancy was uncomplicated.  The infant weighs 3.7 kg (8 lb 3 oz).  Physical examination of the infant is normal.  There is no jaundice or hepatomegaly.  Which of the following is the most appropriate next step in management of this infant?

Accepted Answer

11ec25c8_d6b7_f709_bc81_1fa7237bc23c_MD0003_00 Hepatitis B virus (HBV) can be transmitted vertically from infected pregnant women to their infants. This mother had negative HBsAg testing during the first trimester but became positive for both HBsAg and anti-hepatitis B core antigen (HbcAg) in the third trimester, suggesting she became infected with HBV during her pregnancy. The majority of vertical transmissions occur during the passage of the fetus through the birth canal; in rare cases, transplacental infection can occur, particularly in women with high HBV viral loads or acute infection in the third trimester. Approximately 90% of infants with vertical HBV infection progress to chronic HBV infection, which can lead to cirrhosis, hepatocellular carcinoma, and liver failure. Therefore, newborns of all mothers with active hepatitis B infection should be passively immunized at birth with hepatitis B immune globulin (HBIG), followed by active immunization with recombinant HBV vaccine. These should be administered within 12 hours of birth, regardless of the infant's birth weight or clinical condition. (Choices A and C) Active (HBV vaccine) or passive (HBIG) immunization alone does not provide suitable protection against vertical transmission. Vaccine and immune globulin should always be given together as prophylaxis against HBV for newborns of HBsAg+ mothers. (Choices D and E) Obtaining the infant's serologic status or liver function testing is unnecessary before administering prophylaxis. Infants should have their serologic status checked after the full HBV vaccine series is completed to determine whether they were vertically infected, and infants with confirmed infection should then have liver function tests. (Choice F) HBV infection is not transmitted through breast milk; HIV is the only absolute infectious contraindication to breastfeeding in the developed world. Because this mother is HIV-negative, breastfeeding should be encouraged. Educational objective: Newborns of mothers with hepatitis B virus (HBV) infection should receive passive immunization with hepatitis B immune globulin and active immunization with HBV vaccine within 12 hours of birth. References: Prophylaxis of vertical HBV infection. (http://www.ncbi.nlm.nih.gov/pubmed/27402246)

Question 18

A 6-year-old boy with cystic fibrosis is brought to the office for shortness of breath.  He has had a worsening, productive cough over the past week and now has fever, chills, and difficulty breathing.  His vaccinations are up to date.  Weight is at <5th percentile and height is at the 10th percentile.  His temperature is 38.9 C (102 F), blood pressure is 122/80 mm Hg, pulse is 118/min, and respirations are 28/min.  Pulse oximetry shows an oxygen saturation of 91%.  Physical examination shows a tired-appearing boy with nasal flaring, intercostal retractions, and a barrel-shaped chest.  Auscultation reveals diffuse bilateral wheezing and crackles.  Clubbing of the fingers and toes exhibit  is present.  Sputum culture results are pending.  What is the most likely causative organism of this patient's pneumonia?

Accepted Answer

11ec25c8_d6b5_fb34_bc81_3bd564ea7c01_MD0003_00 Cystic fibrosis (CF) is an autosomal recessive disorder characterized by accumulation of inspissated secretions in multiple organs. Most patients have chronic malabsorption and diarrhea as well as recurrent pneumonias that lead to irreversible bronchiectasis, chronic hypoxia, and progressive respiratory failure. Hyperinflation of the lungs causes the rib cage to remain partially expanded, giving the appearance of a "barrel chest". Bulbous enlargement of the tips of the digits (clubbing) occurs as well. bronchiectasis "barrel chest" Patients with CF are at high risk of infection from unusual and resistant bacteria, viruses, and fungi due to exposure to multiple antibiotic courses. The most common pathogen isolated from sputum cultures in infants and young children is Staphylococcus aureus, a gram-positive coccus that grows in clusters. S aureus colonization decreases with age but remains a significant source of disease in adults with CF. Colonization and infection with Pseudomonas aeruginosa (Choice I) can occur as early as infancy and is the most common cause of CF-related pneumonia in adults. Given its association with a precipitous decline of pulmonary function and increased risk of death, Pseudomonas should be treated for during initial management but is not the most common pathogen in children. (Choice A) Burkholderia cepacia complex refers to several similar species that colonize a small percentage of CF patients. Colonization is associated with accelerated pulmonary decline and decreased survival. (Choices B, C, and H) Patients with deficient cell-mediated immunity (eg, CD4 count <200/µL) are at high risk for fungal pneumonia from Cryptococcus neoformans, Histoplasma capsulatum, and Pneumocystis jirovecii. These fungi are rare in CF; aspergillosis is more common. (Choices D and E) Klebsiella pneumoniae and Legionella pneumophila are gram-negative rods that cause pneumonia but are less commonly implicated in CF. (Choice F) Listeria monocytogenes is a gram-positive rod that causes septicemia and meningitis in neonates and elderly adults. It is an extremely uncommon cause of pneumonia. (Choice G) Nontuberculous mycobacteria (eg, Mycobacterium avium complex, M abscessus) are becoming more prevalent in CF but are still less common than other bacterial pathogens. (Choice K) Streptococcus pneumoniae is the most common cause of pneumonia in otherwise healthy patients. It rarely causes disease in patients with cystic fibrosis, though the pneumococcal vaccine should be administered routinely as in this patient. Educational objective: Staphylococcus aureus is the most common pathogen isolated in infants and young children with cystic fibrosis (CF). Pseudomonas aeruginosa is the most common cause of CF-related pneumonia in adults and contributes to life-threatening decline of pulmonary function. References: Staphylococcus aureus in early cystic fibrosis lung disease. (http://www.ncbi.nlm.nih.gov/pubmed/23970476) Changing Epidemiology of the Respiratory Bacteriology of Patients With Cystic Fibrosis. (http://www.ncbi.nlm.nih.gov/pubmed/26203598)

Question 19

A one-year-old girl is brought to the emergency department (ED) by her mother due to a one-day history of fever and drowsiness.  The child has been irritable since yesterday.  On examination, she is hypothermic, lethargic and has nuchal rigidity.  She flexes her hips when her neck is flexed.  She appears septic, and large petechial and purpuric lesions are developing on her body.  In the ED, she suddenly becomes hypotensive.  Despite aggressive fluid and antibiotic resuscitation, the child dies.  What will most likely be revealed as the cause of death during the autopsy of this child?

Accepted Answer

In an infant with meningococcemia, watch out for Waterhouse-Friderichsen syndrome, which is characterized by a sudden vasomotor collapse and skin rash (i.e., large purpuric lesions on the flanks) due to adrenal hemorrhage. Fulminant meningococcemia can occur after a meningococcus infection, and approximately 10-20% of infants present with vasomotor collapse, large petechiae and purpuric lesions. The condition carries an almost 100% mortality. (Choice A) In meningococcemia, myocarditis does not occur. It can affect the joints, skin and brain, but the heart is spared. (Choice B) Acute respiratory distress syndrome (ARDS) generally does not present in such a dramatic fashion. Rather, it presents with signs of hypoxia and infiltrates on chest x-rays. It is a gradual process where oxygenation becomes increasingly difficult. Most individuals require mechanical ventilation. (Choice C) The bone marrow is not affected by meningococcus. Individuals may show leukocytosis with a leftward shift. (Choice E) Meningococcemia does not directly affect the kidneys. Renal failure may be secondary to sepsis and vasomotor failure, wherein severe vasomotor compromise results in decreased renal perfusion. (Choices F and G) Meningococcemia usually does not cause destruction of the thyroid or liver. Educational Objective: In an infant with meningococcemia, watch out for Waterhouse-Friderichsen syndrome, which is characterized by a sudden vasomotor collapse and skin rash due to adrenal hemorrhage.

Question 20

A 16-year-old girl is brought to the clinic due to vomiting and abdominal pain.  Since this morning, the patient has had multiple episodes of nonbilious, nonbloody emesis as well as intermittent nausea and abdominal pain.  She has also had 3 episodes of watery diarrhea.  The patient attended a school cookout approximately 36 hours prior to her first bout of emesis, and several of her friends who also attended have similar symptoms.  Temperature is 37.4 C (99.1 F), blood pressure is 115/75 mm Hg, and pulse is 95/min.  She appears uncomfortable but is alert and interactive.  Mucous membranes are slightly dry.  There is diffuse tenderness to deep palpation on abdominal examination but no masses or hepatosplenomegaly.  The skin is well perfused, and no rashes are evident.  Which of the following is the most likely etiology of this patient's illness?

Accepted Answer

11ec25c8_d6b3_b140_bc81_2fca3f531c4f_MD0003_00 Norovirus is the most common cause of gastroenteritis in the United States. Very few viral particles are necessary for infection to spread via fecal-oral route, leading to outbreaks (eg, schools, cruise ships, day care facilities). Although person-to-person transmission is most common, norovirus infection can also occur with ingestion of contaminated food, such as shellfish, salad, and fruit. Symptoms typically begin 1-2 days after viral exposure and include nonbloody, nonbilious emesis; watery diarrhea; and abdominal pain. Diarrhea is noninflammatory without blood or mucus in the stool. Fever, headache, and malaise are common. The diagnosis is generally clinical. However, confirmatory testing (ie, detection of norovirus in the stool) may be performed in outbreaks or atypical cases (eg, symptoms >7 days). Fecal leukocytes are not seen. Treatment is supportive with oral or intravenous rehydration therapy depending on severity, and symptom resolution is usually within 2-3 days. Because norovirus is not killed by alcohol-based sanitizer or standard cleaning solutions, prevention includes diligent hand hygiene using soap and water and cleansing of contaminated surfaces with bleach. (Choices A and E) Bacillus cereus and Staphylococcus aureus cause foodborne gastrointestinal illness via ingestion of preformed toxin. Vomiting is the predominant symptom and typically begins within 6 hours of eating the contaminated food. In contrast, this patient developed symptoms 36 hours after the cookout. (Choice C) Rotavirus causes severe vomiting and watery diarrhea in unvaccinated children age ≤2. Infection in adolescents and adults is typically mild or asymptomatic due to the presence of antibodies from prior exposure or vaccination. Rotavirus is less likely than norovirus in this symptomatic, teenage patient. (Choice D) Shigella sonnei presents with abrupt onset of high fever, abdominal cramping, and stools containing mucus and/or blood. This patient is afebrile with watery diarrhea, making norovirus more likely. Educational objective: Norovirus is the most common gastroenteritis in the United States and is often implicated in outbreaks on cruise ships and in schools. Patients develop vomiting, watery diarrhea, and abdominal pain 1-2 days after exposure. Treatment is supportive, and symptoms generally resolve within 2-3 days. References: Human norovirus transmission and evolution in a changing world. (http://www.ncbi.nlm.nih.gov/pubmed/27211790) Norovirus genotype profiles associated with foodborne transmission, 1999-2012. (http://www.ncbi.nlm.nih.gov/pubmed/25811368)

Exam 2: Pediatric