Auto-immune cerebellar ataxia with anti-GAD antibodies accompanied by de novo late-onset type 1 diabetes mellitus

Abstract Autoantibodies to glutamic acid decarboxylase (GAD-Ab) have been described in stiff-man syndrome, type 1 diabetes mellitus and in patients with auto-immune polyglandular failure. In addition, a few patients with progressive cerebellar ataxia show high titres of GAD-Ab, suggesting an auto-immune origin. Aim This is a report of a patient presenting with cerebellar ataxia associated to late-onset type 1 diabetes and polyendocrine auto-immunity. Case report A 47-year-old woman with a past medical history of vitiligo and Graves' disease presented with late-onset type 1 diabetes. For two years, she had complained of progressive gait instability and oscillopsia. Neurological examination revealed multidirectional, horizontal rotatory fixation and gaze nystagmus, gait ataxia and mild limb ataxia in the left upper arm. Methods Imaging studies, electrophysiological studies, routine biological and detailed immunological screening as well as a study of cerebrospinal fluid (CSF) were performed. Results Brain magnetic resonance imaging showed cerebellar atrophy . Routine biological screening was normal. Immunological screening showed positivity for numerous antibodies (Ab), including GAD-Ab, thyroid peroxidase-Ab, thyroglobulin-Ab, 21-hydroxylase (adrenal)-Ab, gastric parietal cell-Ab and GM1 ganglioside IgG-Ab. CSF was normal, with no oligoclonal bands detected. GAD-Ab were positive in CSF, suggesting an auto-immune origin of the cerebellar ataxia. Treatment with intravenous immunoglobulin led to a slight improvement in nystagmus and gait instability. Conclusion Auto-immune cerebellar ataxia related to GAD-Ab is a rare condition that typically affects women with late-onset type 1 diabetes or other auto-immune disorders, including auto-immune polyendocrinopathy. Immunomodulatory treatment may be effective.