Familial hyperinsulinism-hyperammonemia syndrome in a family with seizures: case report

Hyperinsulinism-hyperammonemia (HI/HA) syndrome is the second most frequent cause of congenital hyperinsulinism (CHI) and it is characterized by recurrent symptomatic hypoglycemia and persistent hyperammonemia. We describe the familial case of a 2-year-old child and her 32-year-old mother who, having suffered from tonic-clonic seizures since infancy, had both been diagnosed with epilepsy and treated with sodium valproate. Hypoglycemia was identified in the child in routine analysis. Six days after admission, a complete study of hypoglycemia showed test results compatible with hyperinsulinemic hypoglycemia and hyperammonemia. A mutation in the GDH gene (Arg269His) confirmed the diagnosis in both the mother and the child. An important peculiarity of this case is the diagnosis of a 32-year-old woman, previously diagnosed with epilepsy through her daughter's diagnosis at a Pediatric Endocrinology Department and subsequently treated ineffectively with sodium valproate. We conclude that, as hypoglycemia may be subtle, the diagnosis of HI/HA should be considered in children or adults with seizures/epilepsy and hyperammonemia, serum ammonia being a simple screening test for the disease.