skip to main content

Anti-HMGCR Myopathy — EECC MCQ

Instant feedback + full explanation. One question, done properly.

HardCardiac PharmacologyAnti-HMGCR MyopathyEECC

A 58-year-old man on long-term statin therapy (atorvastatin 80 mg) develops progressive proximal muscle weakness without significant CK elevation. His symptoms persist despite stopping the statin. Anti-HMGCR antibodies are positive. What is the diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Anti-HMGCR antibody-positive immune-mediated necrotising myopathy (IMNM) — a rare autoimmune condition triggered by statin exposure that persists after drug withdrawal and requires immunosuppressive treatment

Anti-HMGCR (anti-3-hydroxy-3-methylglutaryl-CoA reductase) immune-mediated necrotising myopathy is a rare autoimmune condition (~2-3 per 100,000 statin users) characterised by: (1) proximal muscle weakness (progressive, can be severe); (2) elevated CK (often >10x ULN, though can be mildly elevated); (3) positive anti-HMGCR antibodies (specific biomarker); (4) persistence or worsening after statin withdrawal (distinguishing it from typical statin myopathy); (5) necrotising myopathy on muscle biopsy with minimal inflammation. Treatment requires immunosuppression (corticosteroids + methotrexate or IVIG), not simply stopping the statin. The condition is autoimmune — the statin triggers production of antibodies against the HMGCR enzyme (the same enzyme statins target). This is distinct from statin-associated muscle symptoms (SAMS), which resolve after drug discontinuation.

Reference: BSR/BHPR Guidelines; ESC CVD Prevention Guidelines