Inborn Metabolic Diseases

pp 143-149

Persistent Hyperinsulinemic Hypoglycemia

  • Pascale de LonlayAffiliated withUnité de Métabolisme, Département de Pédiatrie, Hôpital Necker-Enfants Malades
  • , Jean-Marie SaudubrayAffiliated withUnité de Métabolisme, Département de Pédiatrie, Hôpital Necker Enfants Malades

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Hyperinsulinism can occur throughout childhood but is most common in infancy. Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is the most important cause of hypoglycemia in early infancy. The excessive secretion of insulin is responsible for profound hypoglycemia and requires aggressive treatment to prevent severe and irreversible brain damage. Onset can be in the neonatal period or later, with the severity of hypoglycemia decreasing with age. PHHI is a heterogeneous disorder with two histopathological lesions, diffuse (DiPHHI) and focal (FoPHHI), which are clinically indistinguishable. FoPHHI is sporadic and characterized by somatic islet-cell hyperplasia. DiPHHI corresponds to a functional abnormality of insulin secretion in the whole pancreas and is most often recessive although rare dominant forms can occur, usually outside the newborn period. Differentiation between focal and diffuse lesions is important because the therapeutic approach and genetic counselling differ radically. PET scanning with 18-fluoro-dopa can distinguish between focal and diffuse PHHI. A combination of glucose and glucagon is started as an emergency treatment as soon as a tentative diagnosis of PHHI is made. This is followed by diazoxide and other medication. Patients who are resistant to medical treatment require pancreatectomy; FoPHHI can be definitively cured by a limited pancreatectomy, but DiPHHI requires a subtotal pancreatectomy, following which there is a high risk of diabetes mellitus. Persistent hyperinsulinism in older children is most commonly caused by pancreatic adenoma.