Increasing recognition of statin-associated anti-HMGCR antibody-positive autoimmune myopathy: a single-center retrospective study

Objective

The use of statins, which are inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) enzyme, may in rare cases be associated with immune-mediated necrotizing myopathy. This condition is characterized by the presence of autoantibodies directed against the HMGCR enzyme. Previously considered very rare, the incidence of this myopathy diagnosis has markedly increased in our rheumatology unit over the past years.

Methods

We conducted a retrospective analysis of 13 patients diagnosed with statin-associated anti-HMGCR antibody (Ab)-positive immune-mediated necrotizing myopathy (anti-HMGCR-IMNM) over the 5-year period (June 2020–May 2025) at the Turku University Hospital’s rheumatology department serving 490,000 inhabitants.

Results

Patients presented with elevated creatine kinase (CK) levels, positive anti-HMGCR-Ab, proximal muscle weakness, and the initial symptom was usually difficulty walking. No other myositis autoantibodies were detected and extra-myopathic symptoms were rare. Most patients responded to immunosuppressive therapy including glucocorticoids, methotrexate or azathioprine, and rituximab with a more severe disease course. Disease severity ranged from mild to fatal. The incidence of statin-associated anti-HMGCR-IMNM was 5.3 cases per million per year, approximately 2.75 per 100,000 statin users per year, higher than previously reported.

Conclusion

Statin-associated anti-HMGCR-IMNM is a rare but increasingly recognized condition requiring early diagnosis and immunosuppressive treatment. The clinical presentation is highly variable. Treatment and its intensity must be tailored individually, taking into account the patient’s comorbidities and treatment related risks.