[A new case of cerebellar ataxia with anti-GAD antibodies treated with corticosteroids and initially seronegative].

Cerebellar ataxia with antiglutamic acid decarboxylase antibodies (GAD-ab) is an exceptional newly recognized autoimmune disorder. The cerebellar ataxia may occur in isolation or be associated with stiff man syndrome another rare GAD-Ab induced disorder of central nervous system. A 38-year-old woman with a past history of Graves disease presented with insidious cerebellar symptoms including ataxic gait, dysmetria, dysarthria, and oscillopsia. A thorough survey of markers of paraneoplastic cerebellar ataxia and collagen diseases was negative. Her serum contained high level of GAD-ab (647.2 U/ml) and MRI evidenced pure cerebellar atrophy leading to diagnosis of autoimmune cerebellar ataxia. Under corticosteroids, cerebellar symptoms partially improved, but serum GAD-ab titre dramatically decreased. Testing for GAD-ab may be indicated in patients with idiopathic cerebellar ataxia, particularly mature women with organ-specific autoimmune diseases. Corticosteroids must be started to prevent irreversible cerebellar atrophy.