A 68-year-old woman presents with fatigue and is found to have haemoglobin 8.5 g/dL, normal WBC, platelets 650,000/µL, and serum ferritin 8 ng/mL. Peripheral smear shows microcytic hypochromic cells. Colonoscopy is negative. Bone marrow biopsy shows hypercellularity with increased megakaryocytes and absent iron stores. JAK2 V617F mutation is positive. The MOST likely diagnosis is:
- A Iron deficiency anaemia alone
- B Essential thrombocythaemia with coincidental iron deficiency
- C Polycythaemia vera with iron deficiency masking erythrocytosis ✓
- D Primary myelofibrosis with thrombocytosis
Correct answer: C. Polycythaemia vera with iron deficiency masking erythrocytosis
Explanation
JAK2 V617F mutation with thrombocytosis, hypercellular marrow with increased megakaryocytes, and absent iron stores in the setting of anaemia is classic for polycythaemia vera (PV) masked by concurrent iron deficiency. PV patients can develop iron deficiency from repeated phlebotomy or chronic GI bleeding, which normalises or lowers the haematocrit, masking the true erythrocytosis. The WHO 2022 diagnostic criteria for PV include JAK2 mutation plus hypercellular marrow; serum EPO levels would be low. This presentation is a classic pitfall in NEET PG.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.