Unusual manifestations in two cases of necrotizing myopathy associated with SRP-antibodies

Anti-SRP (signal recognition particle) positive necrotizing myopathy is commonly not associated with neoplasms. We demonstrate two histologically confirmed cases with unusual manifestations of anti-SRP positive necrotizing myopathy. A 65-year-old man presented with rapidly progressing weakness and mild difficulties in swallowing and speaking. Screening for underlying disorders revealed a moderately differentiated renal adenocarcinoma. The muscular symptoms partially improved after tumor nephrectomy and prednisone treatment. However, the patient developed pulmonary metastases and died of the sequelae of pneumonia 11 months after the diagnosis of renal cancer. The second patient developed rapidly complete external ophthalmoplegia, severe bulbar dysarthrophonia and dysphagia, bilateral facial palsy, loss of patellar and ankle jerk reflexes, and severe symmetrical tetraparesis of both proximal and distal muscles. CSF showed mildly increased protein levels, neurography axonal impairment of motor nerves. Screening revealed no evidence for infections, ganglioside antibodies, and carcinoma. MRI was normal. The disease course suggested an overlap syndrome of Miller-Fisher-syndrome, axonal Guillain-Barré-syndrome and Bickerstaff brainstem encephalitis. In conclusion SRP antibodies might be found in necrotizing myopathies associated with autoimmune mediated overlap syndromes and neoplasms. The pathomechanism is not clear. Any otherwise unexplained evidence of necrotizing myopathy should prompt the screening for SRP antibodies.