Congenital hyperinsulinism in an infant caused by a macroscopic insulin-producing lesion.

Congenital hyperinsulinism is the most common cause of persistent neonatal hypoglycemia. Severe congenital hyperinsulinism is most often due to inactivating mutations in either the ABCC8 or KCNJ11 genes, which encode the SUR1 and Kir6.2 proteins, respectively--the two components of the ATP-sensitive K+ (KATP) channel; neonatal hypoglycemia due to macroscopic insulin-producing pancreatic lesions or adenomas are extremely rare. KATP channel hyperinsulinism is classified as diffuse or focal, the latter being associated with paternally-derived mutations of ABCC8 or KCNJ11 and somatic loss of heterozygosity of the maternal alleles. KATP channelopathies usually produce microscopic intra-pancreatic lesions and are typically unresponsive to drug therapy, requiring > 95% pancreatectomy for diffuse disease and occasionally more limited pancreatic resection for focal disease; macroscopic pancreatic lesions and adenomas are focally excised. We describe a 1 month-old infant with severe congenital hyperinsulinism who had a macroscopic insulin-producing pancreatic lesion successfully treated with focal lesion enucleation.