A case of multiple sclerosis and necrotizing autoimmune myopathy with anti-SRP antibodies

Only few reports exist regarding the coexistence of multiple sclerosis (MS) and autoimmune myopathies. We describe the case of a man with a long history of undiagnosed left lower limb motor impairment who was hospitalized for subacute onset of a myopathic syndrome. In addition, neurological examination revealed sensory impairment and pyramidal signs in the left limbs. Muscle biopsy revealed a necrotizing myopathy and serum anti-signal recognition particle (SRP) antibodies were found. Brain and spinal cord MRI displayed several non-enhancing demyelinating lesions, and CSF-restricted oligoclonal bands were detected. Multimodal evoked potentials showed increased latency of central conduction. Total body PET-CT did not reveal malignancies. A final diagnosis of anti-SRP necrotizing autoimmune myopathy (NAM) and MS was made, and subsequent therapy with azathioprine resulted in a complete stability for both diseases during the follow up. To the best of our knowledge this is the first reported case of concomitant NAM and MS.