Statin-associated necrotising myopathy: higher mortality, largely explained by age and cardiometabolic disease

Design

Retrospective single-centre cohort

Population

142 adults with inflammatory myopathy, 41 with statin-associated IMNM

Primary outcome

All-cause mortality

Effect

31.7% vs 23.8%; unadjusted HR 2.55 (1.24–5.24); fully adjusted HR 1.70 (0.71–4.08)

A US tertiary centre reviewed 142 adults with idiopathic inflammatory myopathy, 41 of whom had immune-mediated necrotising myopathy after recent statin exposure, usually with anti-HMGCR antibodies.

Mortality was 32% in the statin-associated group against 24% in other myositis. The unadjusted hazard of death was about 2.5 times higher, but the difference shrank after adjusting for age and was no longer significant after adjusting for diabetes and hyperlipidaemia. Older patients with statin-associated disease had the poorest survival, and deaths were mainly cardiopulmonary or infective.

The practical point is that these patients are typically older with diabetes and vascular disease — the reason they were on a statin — and that background drives much of their risk. Cardiovascular risk still needs managing after the statin is stopped, using non-statin options where needed.

• Test for anti-HMGCR antibodies in patients with proximal weakness and high CK on or after a statin.
• Stop the statin and refer to rheumatology or neurology when necrotising myopathy is suspected.
• Continue managing cardiovascular risk after stopping the statin, considering non-statin lipid-lowering drugs.
• Watch for infection on immunosuppression, a leading cause of death in this cohort.

Why it matters

The drug is stopped but the reason it was started remains, and that is what these patients mostly die from.

Don't overread it

A single-centre cohort of 41 patients cannot show statin-associated myositis is independently more lethal once comorbidity is accounted for.

The statistics, in plain English

The hazard ratio fell from 2.55 unadjusted to 1.70 (95% CI 0.71 to 4.08) after adjustment — a sign that much of the apparent excess risk came from age and diabetes rather than the myositis subtype.

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