A 5-year-old boy with known HbSS disease presents with sudden extreme pallor and lethargy, having been well a week ago. Hb has fallen from his baseline 7.5 to 3.2 g/dL. Spleen is palpable 2 cm below costal margin, unchanged from previous visits. Reticulocyte count is 0.1%. What is the most likely cause?
- A Parvovirus B19-induced pure red cell aplastic crisis ✓
- B Acute splenic sequestration crisis
- C Acute chest syndrome
- D Hyperhemolytic crisis from G6PD deficiency
Correct answer: A. Parvovirus B19-induced pure red cell aplastic crisis
Explanation
Parvovirus A19 infects erythroid progenitor cells via the P antigen, halting production entirely, so the hallmark is a profound reticulocytopenia with a sharp hemoglobin drop. Sequestration is excluded because the spleen size is unchanged; in sequestration the spleen enlarges rapidly with a falling hemoglobin but the reticulocyte count stays high. Hyperhemolysis also shows brisk reticulocytosis, the opposite finding here.
Reference: Nelson Textbook of Pediatrics, 22nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.