Becker Muscular Dystrophy Accompanied by Anti-HMGCR Antibody-positive Immune-mediated Necrotizing Myopathy.

Becker muscular dystrophy (BMD) is an X-linked neuromuscular disease characterized by progressive muscle weakness that currently has no cure. Immune-mediated necrotizing myopathy (IMNM) is a type of autoimmune inflammatory myopathy characterized by proximal muscle weakness that is treated with immunosuppressive therapy. We herein report a patient diagnosed with BMD complicated with IMNM by a pathological analysis. Notably, the patient had an elevated serum anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody level. Oral glucocorticoid and methotrexate treatment partially improved the muscle weakness with decreased levels of serum creatine kinase. An accurate diagnosis is important for therapeutic decisions in these complicated cases.