Hypoglycaemia due to hyperinsulinism: diagnosis, causes and management

Key words: Hypoglycaemia, Congenital hyperinsulinism, GLUD1 mutation, Case report

The paper describes the case of a 3-month-old girl with seizures due to persistent nonketotic hypoglicaemia with moderate iperammoniaemia. Once tyrosinemia, urea cycle disorders, deficit of fatty-acids-beta-oxidation and other organic acidurias had been excluded, in consideration of the positive response to glucagon test and elevation of alfa-ketoglutaric- acid in urine, a specific form of congenital hyperinsulinaemic hypoglicaemia was suspected. The genetic analysis confirmed a mutation of GLUD1, encoding glutamate dehydrogenase. Clinical response to diazoxide treatment was optimal with normal fasting blood glucose levels. Congenital hyperinsulinaemic hypoglicaemia (CHH) represents a group of clinically, genetically and morphologically heterogeneous disorders, secondary to disregulation of insulin secretion by pancreatic beta-cells. GLUD1 mutations lead to hyperinsulinism/ hyperammonaemia syndrome (HI/HA) characterized by asymptomatic hyperammonaemia, usually diazoxide-responsive symptomatic hypoglycaemia, seizures and learning disabilities. For a timely diagnosis of CHH, a critical sample and a glucagon stimulation test should be performed during hypoglycaemic events. Diazoxide is the firstline drug for management and a trial should be tried to facilitate differential diagnosis of genetic forms. The paper highlights the importance of early identification and appropriate treatment of these patients to prevent severe neurological insult.