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B12 Deficiency in Elderly — RACP Adult Medicine MCQ

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ModerateHaematologyB12 Deficiency in ElderlyRACP Adult Medicine

An 80-year-old woman with RA on methotrexate has Hb 100 g/L, MCV 108 fL (macrocytic). Reticulocyte count is low. B12 is 110 pmol/L (low), folate is 3.5 nmol/L (low-normal). She has angular stomatitis and a smooth tongue. Blood film shows hypersegmented neutrophils and oval macrocytes. What is the most likely diagnosis?

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Correct answer: C — B12 deficiency (megaloblastic anaemia)

Macrocytic anaemia with low B12, hypersegmented neutrophils, and oval macrocytes on blood film is megaloblastic anaemia from B12 deficiency. Methotrexate can cause macrocytosis (folate antagonism) but this patient has B12-specific features (glossitis, hypersegmented neutrophils). Treatment: IM hydroxocobalamin (1 mg on alternate days for 2 weeks, then 1 mg every 3 months lifelong if pernicious anaemia). Check anti-IF antibodies and ensure folate repletion.

Reference: BSH – 2024 – B12 and Folate Deficiency; eTG Haematology 2024