Primary persistent hyperinsulinaemic hypoglycaemia of infancy is rare. Diazoxide treatment remains the mainstay of medical therapy in long-term management. We reviewed 77 cases of primary persistent hyperinsulinism in neonates and infants who were treated with diazoxide and studied criteria predictive of therapeutic efficacy. The only criterion identified was age at manifestation. All but 1 of the 31 neonatal cases were unresponsive to diazoxide. Responsiveness increased with age: 12 of 39 early-infantile cases, and all seven late-infantile cases were diazoxide-responsive. In responders, a diazoxide dose of 10-15 mg/kg per day was always effective, suggesting an "all or none" response. Diazoxide-resistant hyperinsulinism is characterized by its severity with higher plasma insulin levels. The analysis of 46 surgically treated patients showed that the efficacy of diazoxide is not related to the aetiology of the pancreatic lesions. In six cases, after many years of management, diazoxide treatment was stopped without recurrence of hypoglycaemia.
Conclusion: Diazoxide is an efficient treatment in the long-term management of most persistent hyperinsulinaemic hypoglycaemia of infancy revealed in infants and children but is usually ineffective in neonatal forms. Drug efficacy does not correlate with anatomical lesions. Medical treatment can sometimes be stopped after many years of management without recurrence of disease manifestations.