A patient with chronic hemolytic anemia develops an acute aplastic crisis with sudden drop in Hb from 9 to 4 g/dL, reticulocyte count drops to near zero. The most likely cause is:

• A Autoimmune hemolytic exacerbation
• B Folate deficiency superimposed on the chronic hemolysis
• C Hypersplenism developing after splenic sequestration
• D Parvovirus B19 infection interrupting erythropoiesis ✓

Explanation

Aplastic crisis in chronic hemolytic anemias (sickle cell disease, hereditary spherocytosis) is almost always caused by Parvovirus B19, which infects and destroys erythroid progenitor cells by binding to globoside (P antigen). Because these patients depend on accelerated erythropoiesis (shortened RBC survival), even transient arrest of erythropoiesis causes dramatic fall in Hb with near-zero reticulocytes. The crisis is self-limiting in immunocompetent patients as viral immunity is established within 7-10 days.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.