A 4-year-old girl with sickle cell disease is brought to the emergency department with fatigue and loss of appetite. Her parents first noticed her fatigue 3 days ago when she asked to go to sleep earlier than her bedtime. Over the past 2 days, the patient has been drinking well but eating much less than normal. Her father states, "She's been so tired that she wouldn't even get out of bed this morning." She had an episode of acute chest syndrome 2 years prior that required an exchange transfusion. The patient takes folic acid and penicillin. Immunizations are up to date, including the annual influenza vaccine. Temperature is 36.7 C (98 F), blood pressure is 110/65 mm Hg, pulse is 120/min, and respirations are 25/min. Oxygen saturation is 95% on room air. Physical examination shows a pale and tired-appearing girl. Conjunctival pallor is present. Respiratory, abdominal, and neurologic examinations are within normal limits. Laboratory results are as follows: Which of the following is the most likely diagnosis of this patient?

Question

A 4-year-old girl with sickle cell disease is brought to the emergency department with fatigue and loss of appetite.  Her parents first noticed her fatigue 3 days ago when she asked to go to sleep earlier than her bedtime.  Over the past 2 days, the patient has been drinking well but eating much less than normal.  Her father states, "She's been so tired that she wouldn't even get out of bed this morning."  She had an episode of acute chest syndrome 2 years prior that required an exchange transfusion.  The patient takes folic acid and penicillin.  Immunizations are up to date, including the annual influenza vaccine.  Temperature is 36.7 C (98 F), blood pressure is 110/65 mm Hg, pulse is 120/min, and respirations are 25/min.  Oxygen saturation is 95% on room air.  Physical examination shows a pale and tired-appearing girl.  Conjunctival pallor is present.  Respiratory, abdominal, and neurologic examinations are within normal limits.  Laboratory results are as follows:  Which of the following is the most likely diagnosis of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bf7f_3d1d_8f63_31bf94476b0f_MD0005_00 Sickle cell disease (SCD) is characterized by abnormal hemoglobin chains that result in decreased life span of red blood cells and chronic anemia. Patients compensate for this chronic anemia with increased erythropoiesis and an elevated reticulocyte count. An aplastic crisis in SCD is characterized by sudden cessation of erythropoiesis with a very low reticulocyte count (less than <1%) and resultant acute, severe anemia. Parvovirus B19, which preferentially attacks erythroid precursors rather than other cell lines, is the most common cause of an aplastic crisis in SCD. As most children are exposed to and develop immunity against parvovirus by age 15, aplastic crises are rare after early childhood. Blood transfusions are the mainstay of treatment while erythropoiesis recovers. Aplastic crises in SCD differ from aplastic anemia, which occurs in patients without SCD and is characterized by pancytopenia. (Choice A) Acute chest syndrome typically presents with fever, chest pain, and a new pulmonary infiltrate on chest x-ray. This patient is afebrile and has no chest pain or cough. (Choice C) A hyperhemolytic crisis is a very rare complication of SCD that presents with acute, severe anemia and an increased reticulocyte count, which differentiates it from an aplastic crisis. The etiology is unknown. (Choice D) Splenic sequestration is due to pooling of red blood cells in the spleen and presents with a rapidly enlarging spleen. Laboratory findings include severe anemia and marked reticulocytosis. This patient's low reticulocyte count and normal abdominal examination make sequestration unlikely. (Choice E) SCD is the most common cause of stroke in pediatric patients and should be considered in any patient with altered mental status, new focal neurologic deficits, or headache. The absence of focal neurologic deficits and headache, combined with severe anemia, makes stroke unlikely in this patient. Educational objective: An aplastic crisis in sickle cell disease is a transient failure of erythropoiesis most commonly due to parvovirus B19. Presentation includes a sudden drop in hemoglobin and a very low reticulocyte count (<1%). References: Clinical presentations of parvovirus B19 infection. (http://www.ncbi.nlm.nih.gov/pubmed/17304869) Human parvovirus B19: general considerations and impact on patients with sickle-cell disease and thalassemia and on blood transfusions. (http://www.ncbi.nlm.nih.gov/pubmed/21585562)

A 4-Year-Old Girl with Sickle Cell Disease Is Brought to the Emergency