Seizures and diagnostic difficulties in hyperinsulinism-hyperammonemia syndrome

Hyperinsulinism/hyperammonemia (HI/HA) syndrome is a rare disorder presented with recurrent hypoglycemia and elevated serum ammonia, which may lead to development delays, permanent neurologic damages, if it remains underdiagnosed. It is caused by activating mutations in the GLUD1 gene which encodes the intra-mitochondrial enzyme glutamate dehydrogenase (GDH). HI/HA syndrome is considered the second most common form of hyperinsulinism (HI), and usually associated with epileptic seizures, mental retardation and generalized dystonia. We reported a patient who was diagnosed as HI/HA with multiple episodes of seizures; and previously had been diagnosed and treated for epilepsy. She has heterozygous mutation in GLUD1 gene. Treatment with diazoxide enabled complete resolution of the seizures. One year later, when her brother was six months old, he was also diagnosed with HI/HA. Later, the same mutation of GLUD1 was detected in both her father and brother too.