Phenotypical statin‐associated immune‐mediated necrotizing myositis with histological features of inclusion body myositis

Abstract

Abstract Introduction Statin‐associated immune‐mediated necrotizing myositis (IMNM) is a rare but distinct idiopathic inflammatory myopathy (IIM) that requires early recognition and intervention to prevent irreversible muscle damage. It is typically characterized by active statin use, elevated creatinine kinase (CK) levels, proximal muscle weakness, and at times, a positive 3‐hydroxy‐3‐methyl‐glutaryl‐coenzyme A reductase (HMGCR) antibody. Treatment includes immediate discontinuation of the statin and may include corticosteroids, intravenous immunoglobulin (IVIG), and/or immunosuppressive therapy. Inclusion body myositis (IBM), another distinct IIM, also presents with elevated CK levels but with insidious onset of distal upper and proximal lower extremity weakness and is typically refractory to treatment. Case Description A 64‐year‐old female patient presented with proximal muscle weakness, elevated CK levels, and a positive HMGCR antibody in the setting of statin use with muscle pathology suggestive of both statin‐associated IMNM and IBM. She responded to subcutaneous methotrexate and a slow prednisone taper over several months, however, will require close monitoring for symptoms associated with either disease. Conclusion In conclusion, we report a case of muscle weakness with muscle pathology demonstrating both statin‐associated IMNM and IBM. This case highlights the importance of understanding the clinical and pathological features of statin‐associated IMNM and IBM.

Keywords

• 3‐hydroxy‐3‐methyl‐glutaryl‐coenzympe A reductase antibody
• idiopathic inflammatory myopathy
• immune‐mediated necrotizing myositis
• inclusion body myositis
• statin‐associated myositis