An 11-year-old boy with sickle cell disease is brought to the emergency department with worsening shortness of breath, weakness, and fatigue over the past 3 days. The patient has no fever, cough, or chest pain. He has had many hospitalizations for treatment of acute pain and a hospitalization for acute chest syndrome. Temperature is 36.7 C (98 F). Pulse oximetry is 98% on room air. Physical examination shows a pale, tired-appearing boy. Cardiac examination reveals tachycardia; a 3/6 systolic murmur is heard throughout the precordium. The lungs are clear to auscultation. The abdomen is soft and nontender with no palpable liver or spleen. Laboratory results are as follows: Which of the following is the most likely cause of this patient's symptoms?

Question

An 11-year-old boy with sickle cell disease is brought to the emergency department with worsening shortness of breath, weakness, and fatigue over the past 3 days.  The patient has no fever, cough, or chest pain.  He has had many hospitalizations for treatment of acute pain and a hospitalization for acute chest syndrome.  Temperature is 36.7 C (98 F).  Pulse oximetry is 98% on room air.  Physical examination shows a pale, tired-appearing boy.  Cardiac examination reveals tachycardia; a 3/6 systolic murmur is heard throughout the precordium.  The lungs are clear to auscultation.  The abdomen is soft and nontender with no palpable liver or spleen.  Laboratory results are as follows:  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d1ae_bfcf_bc81_c16d940612ab_MD0003_00 Sickle cell disease (SCD) is characterized by chronic anemia with compensatory reticulocytosis. Patients with SCD have increased red blood cell destruction at baseline and are at risk for acutely worsening, severe anemia. An acute drop in hemoglobin accompanied by a low reticulocyte count (<1%) without splenomegaly is consistent with an aplastic crisis, which is characterized by a sudden halt in red blood cell production (erythropoiesis). Anemia is typically severe (<6 g/dL) and patients may have pallor, fatigue, and a functional systolic murmur (due to hyperdynamic blood flow). White blood cell and platelet counts are typically normal. The most common cause of an aplastic crisis is parvovirus B19, which infects and destroys erythrocyte precursors. Aplastic crises generally present before age 15 as parvovirus outbreaks are most common in school-age children. Although erythema infectiosum (ie, fever, rash) is the classic presentation in children, parvovirus B19 infection can result in an aplastic crisis with no preceding viral symptoms. Blood transfusions are the mainstay of treatment. (Choice A) Acute chest syndrome is caused by pulmonary vasoocclusion or infection, and is characterized by fever, chest pain, and a new infiltrate on chest radiograph. Acute chest syndrome is less likely in patients without fever, cough, or chest pain and with clear lungs on auscultation. (Choice B) Aplastic anemia, in contrast to aplastic crisis, causes pancytopenia (eg, thrombocytopenia, anemia, leukopenia) due to bone marrow failure; the name "aplastic anemia" is a misnomer as manifestations are not limited to anemia. Aplastic anemia can be congenital (eg, Fanconi anemia) or acquired (eg, drug-induced, autoimmune). (Choice D) Both primary (eg, idiopathic) and secondary (eg, systemic lupus erythematosus) causes of autoimmune hemolytic anemia present with a dramatic decrease in hemoglobin. However, due to hemolysis, the reticulocyte count is markedly elevated. In addition, patients typically have jaundice due to hyperbilirubinemia from increased red blood cell turnover. (Choice E) Patients with SCD are at risk for cardiac disease due to increased cardiac output secondary to chronic anemia and infarction of myocardial microvasculature. Infarction is more likely in adults and typically presents with chest pain. (Choice F) Splenic sequestration, a condition that occurs in patients with SCD whose spleens have not yet autoinfarcted, is caused by vasoocclusion and pooling of red blood cells in the spleen. Splenic sequestration can cause acute severe anemia; however, patients have an elevated reticulocyte count and a rapidly enlarging spleen. Educational objective: Patients with sickle cell disease can develop aplastic crises characterized by an acute drop in hemoglobin, a reticulocyte count <1%, and no splenomegaly. Parvovirus B19 is the most common cause. 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)

An 11-Year-Old Boy with Sickle Cell Disease Is Brought to the Emergency