Myopathy associated with antibodies to signal recognition particle: disease progression and neurological outcome.

OBJECTIVE To characterize the clinical course of myopathy associated with antibodies to signal recognition particle (SRP), or anti-SRP myopathy. DESIGN Case series. SETTING Keio University Hospitals and National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan. PATIENTS We reviewed clinical features of 27 patients with anti-SRP myopathy and analyzed disease progression and neurological outcome. MAIN OUTCOME MEASURES Anti-SRP antibodies in serum were detected by RNA immunoprecipitation assay using extracts of K562 cells. RESULTS Of the 27 patients, 5 (19%) showed chronic progressive muscle weakness as well as atrophy of limbs and trunk muscles from a younger age with more severe neurological outcomes compared with the other 22 patients(81%) with the subacute form. CONCLUSION A subset of patients with anti-SRP myopathy can show a chronic progressive form associated with severe clinical deficits.