We screened anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies among 42 patients who had undiagnosed chronic myopathy from six national hospitals. Anti-SRP and anti-HMGCR antibodies were determined by RNA immuneprecipitation and enzyme-linked immune-sorbent assay (ELISA), respectively. We identified two patients with anti-SRP antibodies (4.7%) and, two with anti-HMGCR antibodies (4.7%). Both of anti-SRP-positive patients showed dysphagia with a high level of creatine kinase. Anti-HMGCR antibodies were associated with mild muscle weakness with a relatively late disease onset. Our study suggests the importance of autoantibody testing among undiagnosed chronic myopathy.
Keywords: anti-HMGCR antibody; anti-SRP antibody; chronic myopathy; immune-mediated necrotizing myopathy.