Paraneoplastic Stiff Person Syndrome in Early-Stage Breast Cancer with Positive Anti-Amphiphysin Antibodies.

Stiff person syndrome (SPS) is a rare neurologic disorder, characterized by muscle rigidity and spasms. Anti-glutamic acid decarboxylase (anti-GAD) antibodies are associated with the classic form of SPS, while antibodies against amphiphysin are associated with the paraneoplastic form of the disease. We present the case of a patient with paraneoplastic SPS, presenting with muscle cramps of lower extremities that progressed to severe muscle rigidity and spasms, associated with a right breast tumor and positive anti-amphiphysin antibodies.