Focal congenital hyperinsulinism resulting from biallelic loss of function of KCNJ11 gene.

Congenital hyperinsulinism (CHI) characterised by inappropriate secretion of insulin despite low blood glucose can result in irreversible brain damage if not promptly treated. The most common genetic cause of hyperinsulinism is the pathogenic variants in ABCC8 and KCNJ11, causing dysregulated insulin secretion. Rapid testing is crucial for all patients because finding a mutation significantly impacts this condition’s clinical management. We report a rare case of focal CHI after a homozygous KCNJ11 mutation who underwent a selective lesionectomy and required octreotide for euglycaemia.