Statin-Induced Necrotizing Autoimmune Myopathy in a Patient With Complex Diabetes Management.

Background: In rare cases, statin therapy for the reduction of lipid levels may cause muscle-related adverse effects leading to autoimmune myopathy. Statin-induced necrotizing autoimmune myopathy (SINAM) is typically accompanied by symmetrical proximal muscle weakness and elevated creatine phosphokinase (CPK). Glucocorticoids are the first-line treatment, but therapy may escalate to include methotrexate and/or intravenous immune globulin therapy (IVIG).

Case presentation: A male aged 59 years with confirmed atorvastatin adherence for 1 year presented with a 4-month history of fatigue, neuropathy, and progressive proximal muscle weakness. Laboratory tests revealed elevated CPK as high as 12,990 mcg/L. The anti-3-hydroxy-3-methlyglutaryl coenzyme A reductase (anti-HMGCR) antibody test was positive, and the patient started immunosuppressive therapy with IVIG therapy monotherapy (2 g/kg) over 3 days. Gluocorticoid therapy was not used due to difficult to control type 2 diabetes. After hospital discharge, the patient continued monthly IVIG treatment. Following 7 total rounds (6 rounds postadmission) of IVIG, the patient reported an improvement in activity, increased strength in his daily activities, and his CPK level continued decreasing to 680 mcg/L.

Conclusions: Patients presenting with proximal muscle weakness and elevated CPK, even after statin discontinuation, should be considered for a full workup for potential SINAM. The detection of anti-HMGCR antibodies or presence of necrosis on muscle biopsy are necessary for a formal diagnosis. This case displayed success with IVIG monotherapy, although previous research suggests the best chance of muscle symptom improvement is with a combination of a glucocorticoid, methotrexate, and IVIG.