Anti-glutamic Acid Decarboxylase Antibody-associated Cerebellar Ataxia: A Case Report

Anti-glutamic acid decarboxylase antibodies (anti-GAD-ab) are associated with various neurologic conditions. High titers of anti-GAD-abs are observed in stiff person syndrome and subacute cerebellar degeneration. Type 1 diabetes mellitus (T1DM) and other autoimmune endocrinopathies may coexist in patients who are anti-GAD-ab positive. Herein, we describe a 62-year-old female patient with a past medical history of diabetes mellitus (DM) and smoking, presenting with gradual progression of gait ataxia, dizziness, and vertigo for 6 weeks. A neurologic examination revealed gaze-evoked nystagmus and left-sided dysmetria. She could stand up only with double-sided support. Laboratory examinations showed remarkably increased serum and cerebrospinal fluid anti-GAD-ab levels. Cerebral magnetic resonance imaging was unremarkable. Coexisting autoimmune endocrine diseases were also investigated and the patient was also diagnosed as having T1DM and Hashimoto thyroiditis. Paraneoplastic etiologies were excluded. Treatment was starred with intravenous methylprednisolone. Due to a lack of significant clinical improvement, intravenous immunoglobulin (IVIG) was administered. With minimal improvement of gait ataxia, the patient was followed with prednisone 1 g/day for 1 day and then IVIG 400 mg/kg/day for 1 day once per month. Although it is a rare disease, anti-GAD-ab-associated cerebellar ataxia should be considered, especially in female patients with coexisting aucoimmune disorders, for prompt initiation of immunocherapy.