Clinically disparate stiff-person syndrome with GAD65 autoantibody in a father and daughter.

Stiff-person syndrome (SPS) is a sporadic autoimmune disorder characterized by muscle stiffness with painful spasms and usually a high level of GAD65 antibody. The authors report familial SPS associated with GAD65 antibody. The clinical presentations were disparate; the father had an appendicular form of SPS and the daughter's axial SPS presented with episodic opisthotonos.