A 17-year-old boy who presented with acute mononeuropathy was found to have Type 1 diabetes.

Diabetic neuropathy in children and adolescents with Type 1 diabetes mellitus is rare and is usually subclinical and a complication of the late diabetes period. A 17-year-old boy admitted with a right foot drop of sudden onset was diagnosed with peroneal nerve palsy. He had had osmotic polyuria, polydipsia and weight loss for the past 2 months; his blood glucose was 25 mmol/L (<7.8), HbA1c 15.2% (4.0-5.6) and vitamin B12 125 pg/ml (180-914). The peroneal nerve palsy resolved within 3 months with blood glucose regulation and B12 supplementation. Diabetes should be borne in mind in the differential diagnosis of unusual cases of mononeuropathy.Abbreviations: DCCTS: Diabetes Control and Complications Trial Study; DM: diabetes mellitus; DN: diabetic neuropathy; GAD: glutamic acid decarboxylase; PN: peripheral neuropathy; T1DM: Type 1 diabetes mellitus.