A four-year-old female who was born term via spontaneous vaginal delivery (SVD) with a birth weight of 3.4 kg had an onset of persistent hypoglycaemia at the 6th hour of life. She was diagnosed with congenital hyperinsulinism based on high glucose load, negative ketone and a good response to glucagon. Genetic workup revealed the presence of ATP Binding Cassette Subfamily C Member 8 (ABCC8 genes) mutation which indicated a focal form of congenital hyperinsulinism. She was resistant to the standard dose of oral diazoxide but responded to subcutaneous somatostatin. At the age of 3 years and 6 months, multiple daily injections of somatostatin were replaced with a long-acting monthly somatostatin analogue. With the present treatment, she had better glycaemic control, normal growth and was able to stop tube feeding.
Hyperinsulinism-hyperammonemia syndrome (HI/HA) (OMIM 606762), the second most common form of congenital hyperinsulinism (CHI) is associated with activating missense mutations in the GLUD1 gene, which encodes the mitochondrial matrix enzyme, glutamate dehydrogenase (GDH). Patients present with recurrent symptomatic postprandial hypoglycemia following protein-rich meals (leucine-sensitive hypoglycemia) as well as fasting hypoglycemia accompanied by asymptomatic elevations of plasma ammonia. In contrast to other forms of CHI, the phenotype is reported to be milder thus escaping recognition for the first few months of life. Early diagnosis and appropriate management are essential to avoid the neurodevelopmental consequences including epilepsy and learning disabilities which are prevalent in this disorder. We report an infant presenting with afebrile seizures secondary to hyperinsulinemic hypoglycemia resulting from a novel de novo mutation of the GLUD1 gene.