Myoclonic encephalopathy and diabetes mellitus in a boy

We describe an 18-month-old boy with insulin-dependent diabetes mellitus wh o developed idiopathic myoclonic encephalopathy (dancing eye syndrome) at 2 6 months of age, The neurological symptomatology (multifocal myoclonus, ops oclonus, ataxia, behavioural disturbance) developed within 10 to 14 days af ter presentation. Biological, neuroradiological, and scintigraphic examinat ion excluded CNS infectious diseases, intoxication, or tumours. At onset of diabetes mellitus, anti-glutamic-acid decarboxylase (GAD) antibodies were observed, and markedly increased in titre when myoclonic encephalopathy occ urred. Corticosteroid treatment resulted in a decrease in anti-GAD autoanti body titres and the disappearance of neurological disturbances. As GAD is e xpressed both in pancreatic beta-cells and cerebellar Purkinje cells, it is possible that a common autoimmune disorder in this patient may account for both the diabetes and myoclonic encephalopathy.