A 34-year-old man on zidovudine based antiretroviral therapy presents with increasing fatigue over three months. Haemoglobin is 7.8 g/dL, MCV is 112 fL, and reticulocyte count is low. Bone marrow shows megaloblastic changes. The most likely cause is:

• A Concomitant iron deficiency
• B Zidovudine induced bone marrow suppression ✓
• C Parvovirus B19 induced pure red cell aplasia
• D Immune haemolysis

Explanation

Zidovudine is the NRTI best known for myelosuppression because its triphosphate also inhibits host mitochondrial DNA polymerase gamma to some degree. The classic presentation is macrocytic anaemia with megaloblastic marrow changes, often with neutropenia, typically after weeks to months of therapy and more likely with advanced HIV or low baseline counts. Parvovirus A19 causes pure red cell aplasia without macrocytosis or megaloblastic changes.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.