P.89 Immune-mediated necrotizing myopathy associated with anti-SRP Antibodies: Three cases in Korea

Abstract

Immune-mediated necrotizing myopathy associated with anti-SRP antibodies (anti-SRP myopathy) is characterized by progressive proximal muscle weakness and markedly elevated creatinine kinase (CK. Here, we report the clinical features of three Korean patient with anti-SRP myopathy. A 63-year-old man presented with progressive proximal muscle weakness and dysphagia. He showed symmetrical proximal weakness. The serum CK was 5,560U/L. The muscle biopsy of the biceps brachii showed mild muscle fiber size variation and a few degenerating muscle fibers. Muscle weakness and dysphagia improved after using steroids and azathioprine, but gradually worsen. At the last follow-up study, serum CK was 1,252 IU/L and the serum anti-SRP antibody was positive. A 46-year-old man was referred to our clinic due to progressive proximal muscle weakness. The serum CK was 6,114 U/L. The muscle biopsy of the vastus lateralis muscle showed marked size variation in muscle fibers and many necrotic fibers. Steroid pulse therapy lowered serum CK level, but muscle weakness did not improve. The serum anti- SRP antibody was positive. After the diagnosis, steroid, methotrexate, and intravenous immunoglobulin were used, but his muscle strength did not improve significantly. 43-year-old woman presented with proximal muscle weakness and elevated serum CK level. The serum CK was greater than 13,000 U/L. Needle EMG showed active generalized myopathy. The muscle biopsy of vastus lateralis muscle revealed a few necrotic fibers without endomysial inflammatory cell infiltration. The serum anti-SRP antibody was positive. After steroid pulse therapy, her muscle weakness did not improve and dysphagia was newly developed. She was currently treated with steroid and azathioprine. Anti-SRP myopathy is one of the most disabling and less responsiveness to treatment and we would like to report cases have rarely been reported in Korea.