Anti-HMGCR myopathy frequently coexists with other myositis-specific autoantibodies

To understand the characteristics of Korean patients with anti-HMGCR myopathy, we measured anti-HMGCR antibodies and analyzed clinical, radiological, and pathological features. We measured titers of anti-HMGCR antibodies in the sera of 99 patients with inflammatory myopathy using the enzyme-linked immunosorbent assay. We tested 16 myositis-specific autoantibodies (MSAs) in all patients with anti-HMGCR myopathy. Positivity for the anti-HMGCR antibody was observed in 17 (4 males and 13 females) of 99 patients with inflammatory myopathy. The median age at symptom onset was 60 years. Ten (59%) of the anti-HMGCR positive patients had taken statins. The most common symptoms were proximal muscle weakness in 15 (88%), followed by myalgia in 9 (53%), neck weakness in 4 (24%), dysphagia in 3 (18%), and skin lesions in 2 (12%). The median titer of anti-HMGCR antibody was 202 U/ml. We found eight different MSAs in nine (53%) patients. The median disease duration from symptom onset to diagnosis was significantly shorter in the MSA-positive group than in the MSA-negative group (p = 0.027). In conclusion, our study is the first to measure anti-HMGCR antibodies with inflammatory myopathy, and identify new findings including the coexistence of other MSAs in Korean patients.