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  • Updated 10.19.2020
  • Released 10.19.2020
  • Expires For CME 10.19.2023

GAD antibody-spectrum disorders



The article describes the clinical phenotypes associated with anti-GAD antibodies as distinctly evolved the last decade, their underlying pathophysiology, the significance of anti-GAD antibody titers in clinical diagnosis, and the current therapeutic approaches.

Historical note and terminology

Glutamic acid decarboxylase (GAD) is a pyridoxal 5’-phosphate-dependent enzyme that catalyzes the conversion of the excitatory neurotransmitter l-glutamate to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). The enzyme is widely expressed within the central nervous system and pancreatic beta-cells but is also found in lower amounts in the liver, kidneys, adrenal glands, ovaries, and testes (48). The presence of autoantibodies against GAD was first described in 1988 by Solimena and colleagues in a 49-year-old woman with stiff-person syndrome, epilepsy, and type-1 diabetes mellitus. They detected anti-GAD antibodies in both serum and cerebrospinal fluid and identified for the first time the immunostaining pattern of these antibodies, pointing out the possible immunological connection between stiff-person syndrome and type 1 diabetes mellitus. They concluded that the clinical manifestations of stiff-person syndrome are related to disruption of GABAergic pathways, a notion that it is still valid today (102).

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