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SCD B12 Myelopathy — RACP Adult Medicine MCQ

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ModerateNeurologySCD B12 MyelopathyRACP Adult Medicine

A 55-year-old man presents with progressive spastic paraparesis over 2 years. MRI thoracic spine shows dorsolateral cord signal change. Serum B12 is 80 pmol/L (severely low). Methylmalonic acid and homocysteine are elevated. Anti-intrinsic factor antibody is positive. What is the most likely diagnosis?

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Correct answer: B — Subacute combined degeneration (B12 deficiency)

Progressive spastic paraparesis with dorsal column signs (loss of proprioception and vibration), dorsolateral cord signal change on MRI, and severely low B12 with elevated MMA/homocysteine and positive IF antibody is subacute combined degeneration of the cord from pernicious anaemia. Urgent IM hydroxocobalamin replacement is required. Neurological recovery depends on duration and severity — early treatment improves outcomes.

Reference: eTG Neurology – 2024 – Myelopathy; BSH 2024 B12 Deficiency