We report a patient who developed stiff-man syndrome, including disabling 
shoulder subluxation and wrist ankylosis, in association with breast cancer. 
Immunologic investigations disclosed autoimmunity directed against not only 
glutamic acid decarboxylase but also amphiphysin, a 128-kd protein located in 
the presynaptic compartment of neurons. The patient improved after surgery and 
corticosteroid treatment and has been stable for nearly 4 years on only 
anti-estrogenics. The triad of stiff-man syndrome, breast cancer, and 
autoantibodies against amphiphysin identifies a new autoimmune paraneoplastic 
syndrome of the CNS.