We report the response to sulfonylurea treatment in a boy with neonatal diabetes and marked developmental delay resulting from the KCNJ11 mutation V59M.
In contrast, developmental delay in addition to diabetes was seen in four of five probands with the V59M mutation and two of four with the R201C mutation.
Four of the five patients with mutations had neurological features: the patient with the C166F mutation had marked developmental delay, severe generalised epilepsy, hypotonia and muscle weakness; mild developmental delay was present in the patient with the V59M mutation; one patient with the R201H mutation had acute and chronic neurological consequences of cerebral oedema and another had diabetic neuropathy from chronic hyperglycaemia.