Background Hyperinsulinism, although rare (1:30,000 to 1:50,000 live births), is the most common cause of persistent hypoglycaemia in early infancy. The inappropriate oversecretion of insulin is responsible for profound hypoglycaemia that can cause irreversible brain damage. Seizures are the revealing symptom in approximately half of the cases of persistent hyperinsulinemic hypoglycaemia of infancy (PHHI). Hypoglycaemia of neonatal onset seems to be more severe than infant-onset hypoglycaemia. Diazoxide treatment remains the mainstay of medical therapy in long-term management.

Case report We reprot on an 8-month-old child admitted with a complex seizure. Retrospectively he had possible seizures in the last month and a poor weight and development evolution in the previous two months. His blood glucose level was 37 mg/dl. Because of the high insulin level during hypoglycaemia (insulin/glucose >0.3, insulin: 20.5 μUI/ml), the absence of ketonuria, and the need for a high dose glucose infusion to achieve normoglycaemia, a diagnosis of PHHI was made. He started diazoxide with good therapeutic response. The child is now in the fourteenth month of diazoxide therapy, with good glycaemic control and has a mild development delay.

Discussion PHHI is serious and often difficult to diagnose. Diagnostic criteria and therapeutic management are important to discuss in face of the rarity of these cases and few consensus reports.