GAD1 and diabetes mellitus: The cause of stiff-person syndrome is unknown but an auto-immune pathogenesis is suspected because of the presence of antibodies against glutamic acid decaroxylase (GAD), the rate-limiting enzyme for synthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) [1,5], and the association with other auto-immune diseases such as diabetes and thyroiditis [6].