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 postoperative 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.