The patient in this vignette presents with an isolated decrease in erythrocytes and erythroid precursors suggestive of pure red cell aplasia (PRCA). Parvovirus B19 is known to cause PRCA in addition to erythema infectiosum (Fifth disease).
Hematologic labs reveal a normocytic anemia (MCV between 80 and 100 fL/cell) with an inappropriately low reticulocyte count and normal platelet and leukocyte levels, consistent with PRCA. This condition is characterized by a failure of the bone marrow to produce cells of the RBC lineage without affecting leukocyte precursors or megakaryocytes. Causes of PRCA include: parvovirus B19 infection, thymoma, autoimmune disorders (e.g., systemic lupus erythematosus), and anti-EPO antibodies following prolonged EPO administration. A bone marrow biopsy in patients with PRCA will demonstrate decreased erythrocyte precursors with normal leukocyte and megakaryocyte precursors.
Answer 1: Kaposi’s sarcoma is a malignant neoplasm of lymphatic endothelial cells that is caused by human herpesvirus 8 (HHV-8). It primarily affects AIDS patients but can also be seen in other immunosuppressed patients and in sporadic cases (primarily in older men of Mediterranean origin). HHV-8 is not associated with PRCA.
Answer 3: Mononucleosis is a common systemic syndrome characterized by fatigue, fevers, chills, and lymphadenopathy. The most common causes of mononucleosis are Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Neither of these is associated with PRCA.
Answer 4: Croup presents with wheezing and a barking cough in infants and young children. The most common causes of croup are parainfluenza and respiratory syncytial virus (RSV). Neither of these is associated with PRCA.
Answer 5: Myocarditis presents with dyspnea, chest pain, decreased exercise tolerance, and arrhythmias. The most common viral cause of myocarditis is coxsackievirus. Coxsackievirus is also associated with aseptic meningitis and hand, foot, and mouth disease. However, it is not associated with PRCA.
Pure red cell aplasia is characterized by an isolated decrease in erythrocytes and erythroid precursors with normal levels of leukocytes and platelets. Causes include parvovirus B19, thymoma, autoimmune conditions, and anti-EPO antibodies.