A patient with sickle cell disease develops acute severe back pain, fever, and a rapidly falling hemoglobin from 9 g/dL to 4 g/dL over 24 hours. Reticulocyte count is 0.2%. LDH is minimally elevated. What is the most likely diagnosis?
- A Acute chest syndrome
- B Splenic sequestration crisis
- C Aplastic crisis due to parvovirus B19 infection ✓
- D Hyperhemolytic crisis due to alloantibody-mediated destruction
Explanation
A precipitous fall in hemoglobin with a near-absent reticulocyte count (reticulocytopenia) in a sickle cell patient indicates aplastic crisis due to parvovirus B19. The virus infects erythroid progenitor cells (expressing globoside receptor) and temporarily abrogates red cell production. Since SCD patients have shortened RBC survival and rely on compensatory erythropoiesis, even transient marrow suppression causes rapid, severe anemia. In splenic sequestration, the reticulocyte count is elevated and spleen rapidly enlarges. Hyperhemolytic crisis shows reticulocytopenia but with dramatically elevated LDH and bilirubin due to accelerated destruction. Acute chest syndrome presents with pulmonary symptoms.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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