A patient with chronic haemolytic anaemia develops severe aplastic crisis with a sudden drop in haemoglobin to 4 g/dL. Reticulocyte count is 0.2%. The most likely responsible pathogen is:
- A Epstein-Barr virus
- B Parvovirus B19 ✓
- C Plasmodium falciparum
- D Human herpesvirus 6
Explanation
Parvovirus B19 infects and lyses erythroid progenitors (BFU-E and CFU-E) by binding P antigen (globoside) on their surface. This causes transient arrest of red cell production (pure red cell aplasia) lasting 7–10 days. In patients with normal red cell lifespan this is subclinical, but in patients with chronic haemolytic anaemias (sickle cell, hereditary spherocytosis, thalassaemia) where red cell survival is markedly shortened (20–30 days), even a brief cessation of erythropoiesis precipitates life-threatening aplastic crisis with profound reticulocytopaenia (reticulocyte count near zero). The diagnosis is confirmed by parvovirus B19 PCR or IgM antibodies.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.