A 12-year-old girl is brought to the emergency department due to several days of worsening exertional dyspnea and lethargy. The patient has a history of sickle cell disease and takes hydroxyurea. Physical examination shows mucosal pallor and a systolic ejection murmur. Laboratory studies reveal a hemoglobin level of 5.6 g/dL. Bone marrow biopsy is performed and demonstrates decreased erythroid precursors and giant pronormoblasts containing inclusions, as shown below. Which of the following is the most likely cause of this patient's current condition?

Question

A 12-year-old girl is brought to the emergency department due to several days of worsening exertional dyspnea and lethargy.  The patient has a history of sickle cell disease and takes hydroxyurea.  Physical examination shows mucosal pallor and a systolic ejection murmur.  Laboratory studies reveal a hemoglobin level of 5.6 g/dL.  Bone marrow biopsy is performed and demonstrates decreased erythroid precursors and giant pronormoblasts containing inclusions, as shown below.  Which of the following is the most likely cause of this patient's current condition?

Quizplus · Accepted Answer

11ec160b_3996_d466_9249_8538c6881195_MD0001_00 This patient's symptomatic anemia (lethargy, exertional dyspnea, mucosal pallor, ejection murmur) and bone marrow biopsy showing decreased erythropoiesis (reduced erythrocyte precursors) raise suspicion for transient aplastic crisis due to acute parvovirus B19 infection. Parvovirus is a small, nonenveloped, DNA virus transmitted via the respiratory route that primarily attacks erythroid progenitor cells due to tropism for an erythrocyte cell surface receptor (P blood group antigen). Infection of erythroid progenitor cells prevents red blood cell maturation, leading to formation of abnormal giant pronormoblasts (several times larger than surrounding red blood cells) with glassy, intranuclear viral inclusions. The drop in red cell production often leads to a transient (1-2 week) drop in hematocrit. Although many patients are asymptomatic, individuals with underlying hemoglobin disorders (eg, sickle cell anemia) sometimes develop symptomatic anemia. (Choice B) Folate deficiency can be seen in patients with sickle cell disease due to increased erythropoiesis in response to chronic anemia. However, folate deficiency is characterized by macrocytic anemia and hypersegmented neutrophils; giant pronormoblasts with inclusions would not be seen. (Choice C) Hydroxyurea can sometimes interfere with normal erythropoiesis and result in macrocytic anemia. However, it is not associated with giant pronormoblasts with intranuclear inclusions. (Choice D) Patients with sickle cell disease who require repeated blood transfusion can sometimes develop secondary iron overload. Bone marrow biopsy would show increased iron stores. (Choice E) Exposure to toxic chemicals (eg, industrial solvents/chemicals, insecticides) can lead to aplastic anemia. However, bone marrow biopsy would show hypocellular marrow with a decrease in all cell types; the remaining hematopoietic cells would be morphologically normal. Educational objective: Parvovirus B19 infection can cause transient aplastic crisis, particularly in those with underlying hemoglobin disorders such as sickle cell anemia. Patients develop symptomatic anemia (eg, exertional dyspnea, fatigue, low hematocrit) due to inhibition of erythropoiesis by the virus. Bone marrow examination will show giant pronormoblasts with glassy, intranuclear viral inclusions.

A 12-Year-Old Girl Is Brought to the Emergency Department Due