Glutamic acid decarboxylase (GAD) is the enzyme which catalyzes the production of gamma aminobutyric acid (GABA), the main inhibitory neurotransmitter in the central nervous system (CNS). There is increasing evidence that severe GAD autoimmunity may be associated with refractory epilepsy. Immunomodulation and GABAergic drugs have been suggested as treatment options. We report here for the first time on a patient with sudden onset of refractory status epilepticus in the presence of strong intrathecal anti-GAD antibody synthesis who was successfully treated with cyclophosphamide, and give an overview of available data on epilepsy associated with GAD autoimmunity.