Paraneoplastic Anti-3-hydroxy-3-methylglutary-coenzyme A Reductase Antibody-positive Immune-mediated Necrotizing Myopathy in a Patient with Uterine Cancer

We report the case of a 69-year-old woman with proximal limb muscle weakness, who received post-operative chemotherapy for uterine cancer. Her serum creatinine kinase level was high (10,779 mg/dL) and a muscle biopsy from her left biceps revealed various sizes of muscle fibers accompanied by necrotic and regenerating fibers. She was positive for anti-3 hydroxy-3-methylglutary-coenzyme A reductase (anti-HMGCR) antibodies, but negative for anti-signal recognition particle (anti-SRP) antibodies. She was diagnosed with immune-mediated necrotizing myopathy (IMNM) and treated with prednisolone. Our findings indicate that not only drug-induced myopathy but also paraneoplastic myopathy can be involved in the pathogenesis of IMNM.