Severe Hyperinsulinemic Hypoglycemia in a Neonate: Response to Sirolimus Therapy

Hyperinsulinemic hypoglycemia (HH) is one of the most common causes of persistent hypoglycemic episodes in neonates. Current pharmacologic treatment of neonatal HH includes diazoxide and octreotide, whereas for diffuse, unresponsive cases a subtotal pancreatectomy may be the last resort, with questionable efficacy. Here we report a case of congenital diffuse neonatal HH, first suspected when severe hypoglycemia presented with extremely high serum insulin levels immediately after birth. Functional imaging and genetic tests later confirmed the diagnosis. Failure to respond to a sequence of different treatments and to avoid extensive surgery with predictable morbidity prompted us to introduce a recently suggested alternative therapy with sirolimus, a mammalian target of rapamycin inhibitor. Glucose intake could be reduced gradually while euglycemia was maintained, and we were able to achieve exclusively enteral feeding within 6 weeks. Sirolimus was found to be effective and well tolerated, with no major adverse side effects attributable to its administration.