Rhabdomyolysis and paraneoplastic stiff‐man syndrome with amphiphysin autoimmunity

Stiff-Man syndrome (SMS) is a rare disease of the central nervous system characterized by chronic muscle rigidity and autoimmunity directed against synaptic antigens. In a subset of patients, generally positive for antiamphiphysin autoantibodies, SMS has an autoimmune paraneoplastic origin. Amphiphysin isoforms are expressed at high levels in brain and skeletal muscle and often are overexpressed in breast cancer. We report here the occurrence of rhabdomyolysis in a patient with SMS, breast cancer, and antibodies that recognize both brain and muscle amphiphysin isoforms. Immunotherapy induced a remission of both rhabdomyolysis and SMS symptoms. Autoimmune rhabdomyolysis may represent a paraneoplastic complication of cancer patients with amphiphysin autoimmunity.