Hyperammonemia and positive allopurinol test in hyperinsulinism- hyperammonemia syndrome: Taiwanese case report

Hyperinsulinismhyperammonemia syndrome (HHS; M606762) is a recently identified metabolic disease. Affected patients have symptomatic hypoglycemia with moderate, usually asymptomatic hyperammonemia.1 Stanley et al. found that their HHS patients had a mutation of glutamate dehydrogenase (GDH) gene, and reported this as the cause.2 This gene defect leads to excessive activity of GDH. This impairs responsiveness to allosteric inhibition by guanosine triphosphate (GTP), and simultaneously increases pancreatic beta cell insulin release, and impairs the livers ability to detoxify ammonia.2 In these patients leucine acts as an activator of GDH, resulting in hyperinsulinism. Although not specific, the allopurinol test is regularly used in cases of hyperammonemia to diagnose ornithine transcarbamylase (OTC) deficiency.3 To date there has been no documentation of a positive allopurinol test in HHS. Here, we report a Taiwanese girl with a positive allopurinol test, who had elevated urine orotic acid level with HHS. Afterward, we compared her clinical manifestations and laboratory findings with those of her affected family members. Comparison of the clinical findings of HHS with previous reports is discussed. ? 2009 Japan Pediatric Society.