Parvovirus Aplastic Crisis — RACP Adult Medicine MCQ

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ModerateHaematologyParvovirus Aplastic CrisisRACP Adult Medicine

A 45-year-old woman with known hereditary spherocytosis (HS) develops sudden onset severe anaemia (Hb drops from 110 to 50 g/L over 48 hours). Her reticulocyte count is 0% (absent). She has a mild viral illness. What is the diagnosis?

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Correct answer: B — Aplastic crisis from parvovirus B19 infection

In chronic haemolytic disorders (hereditary spherocytosis, sickle cell disease, thalassaemia), parvovirus B19 infection causes a transient aplastic crisis by directly infecting and destroying erythroid precursors in the bone marrow. The hallmark is sudden severe anaemia with absent reticulocytes (reticulocyte count ~0%) – the reticulocytosis that normally compensates for chronic haemolysis disappears. Recovery occurs spontaneously within 7–10 days as anti-B19 antibodies develop. Red cell transfusion may be needed. Parvovirus B19 IgM confirms acute infection.

Reference: eTG – 2025 – Haematology