Anti-SRP Myopathy: Disease Progression and Neurological Outcome (PD6.010)

Abstract

Objective: To characterize the clinical course of anti-signal recognition particle (SRP) myopathy. Background Anti-SRP myopathy has recently been regarded as an immune-mediated necrotizing myopathy with severe muscle weakness. The rapid progression of weakness is a characteristic clinical feature of anti-SRP myopathy. However, patients with anti-SRP myopathy can show chronic progression indistinguishable from muscular dystrophy. Design/Methods: We reviewed clinical features of 27 patients with anti-SRP myopathy, and analyzed disease progression and neurological outcome. Anti-SRP antibodies in serum were detected by RNA immunoprecipitation assay using extracts of K562 cells. Neurological outcome were divided into three groups: recovered, mild deficit, and severe deficit. Results: We divided 27 patients with anti-SRP myopathy into two subtypes-subacute and chronic forms-based on the clinical course. Five (18.5%) were considered to have the chronic form. Disease onset occurred at a younger age in those with the chronic form than in those with the subacute form (15.4 versus 52.4 years of age, p = 0.0001). Lower limbs were more severely affected than upper limbs. All 5 patients with the chronic form and about half of the patients with the subacute form showed severe muscle weakness and atrophy at the first examination. Twenty-six percent of the patients suffered dysphagia and 11% reported it as the initial symptom. Extramuscular manifestations were observed only in patients with the subacute form. Serum CK levels were markedly elevated to more than 1,000 IU/L. All patients were treated with oral prednisolone. Half of the patients were treated with additional immunosuppressive agents. The neurological outcomes showed that 45% of patients with the subacute form recovered. In contrast, all 5 patients with the chronic form had more severe neurological outcomes compared to the 22 patients with the subacute form. Conclusions: A subset of patients with anti-SRP myopathy can show a chronic progressive form associated with severe clinical deficits. Disclosure: Dr. Suzuki has nothing to disclose. Dr. Hayashi has nothing to disclose. Dr. Kuwana has nothing to disclose. Dr. Tsuburaya has nothing to disclose. Dr. Suzuki has nothing to disclose. Dr. Nishino has nothing to disclose.