Case report: focal nesidioblastosis ("nesidioblastoma") in an adult.

Adult nesidioblastosis is an uncommon cause of hyperinsulinemic hypoglycemia characterized by diffuse islet hyperplasia with beta-cell hypertrophy and atypia. The cause of nesidioblastosis in adults is unclear but may be different from nesidioblastosis in infants. In contrast to infants, a focal form of adult nesidioblastosis (ie, "nesidioblastoma") has not been documented, although proposed. We report a 44-year-old man with symptomatic hypoglycemia and localized nesidioblastosis treated with surgical enucleation resulting in normalization of blood glucose. Postoperative euglycemia has persisted in this patient to date (4 months at the time of manuscript submission).