Stiff-person syndrome associated with cerebellar ataxia and high glutamic acid decarboxylase antibody titer

Glutamic acid decarboxylase (GAD) is the main target of humoral autoimmunit y in patients with insulin-dependent diabetes mellitus (IDDM) and stiff-per son syndrome. We reviewed the case of a 46-year-old woman who had cerebella r ataxia before getting stiff-person syndrome and IDDM with high anti-GAD a utoantibody titers. This was a rare case in which there were both the clini cal symptoms of stiff-person syndrome and cerebellar ataxia. In western blo t analysis her serum reacted with 65-kDa proteins from rat cerebellum, cere bral cortex, and spinal cord. Autoantibodies to GAD may cause functional im pairment of gamma -aminobutyric acid (GABA) neurons in the spinal cord as w ell as in the cerebellum.