High Titer of Circulating Antiglutamic Acid Decarboxylase Antibodies in a Patient with Cerebellar Ataxia and Type 1 Diabetes.

A 24-year-old female who was recently diagnosed with Type 1 diabetes mellitus (TiD) presented with a five-year history of visible gait disturbance and slurred speech. Her neurologic examination was remarkable for dysarthria, bilateral nystagmus, dysdiadochokinesia, finger-nose incoordination, heel-knee incoordination, and ataxic gait. A brain MRI disclosed diffuse cerebellar atrophy. Her serum antiglutamic acid decarboxylase (GAD) antibody titer was elevated. Antinuclear antibody (ANA) test was positive with atiterofl:2560 and a speckledpattern. Genetictests for inherited ataxia, including Friedreich ataxia, were negative for mutations. Her cerebrospinal fluid (CSF) analysis revealed oligoclonal bands and she had a positive CSF GAD65 antibody. A diag- nosis of GAD antibody-induced cerebellar ataxia was considered. She developed GAD autoimmune antibody positive TiD during the course ofher dis- ease. GAD antibody-associated cerebellar ataxia is a rare entity, however it should be considered as a possibility in patients with associated autoimmune disease and positive anti-GAD antibody.