Insulin-dependent diabetes mellitus presenting with ketoalkalosis in Rett syndrome.

A 9-year-old girl with Rett syndrome presented with typical symptoms of insulin-dependent diabetes mellitus. Upon investigation she was found to have a primary respiratory alkalosis associated with diabetes ketoacidaemia. Once non-ketotic normoglycaemia was achieved her respiratory alkalosis persisted. This was felt to be due to an abnormal breathing pattern of hyperventilation punctuated by apnoeas which is associated with Rett syndrome.