The Heterogeneity of Focal Forms of Congenital Hyperinsulinism

Background: Congenital hyperinsulinism (CHI) is a cause of persistent hypoglycemia due to unregulated insulin secretion from pancreatic beta-cells. Histologically, there are two major subgroups, focal and diffuse. Focal CHI is typically unresponsive to diazoxide and can be cured with surgical removal of the focal lesion. Aims: We report on three patients with focal CHI to illustrate the marked clinical, genetic, radiological, and histological heterogeneity. Methods and Results: The first two patients had focal CHI due to a paternal (c.3992-9G -> A) ABCC8 mutation. One of these patients was fully responsive to a small dose (5 mg/kg . d) of diazoxide, whereas the other patient was medically unresponsive. In both patients, the focal lesions were accurately localized preoperatively by [F-18] dihydroxyphenylalanine (DOPA) positron emission tomography (PET) and surgically resected. The third patient had a paternally inherited ABCC8 (A1493T) mutation, and the initial [F-18] DOPA PET scan indicated extensive uptake of DOPA in the body and tail of the pancreas. However, despite surgical resection of the body and tail, this patient continued to have severe CHI. A subsequent [F-18] DOPA PET scan now showed markedly increased DOPA uptake in the remaining body and head of the pancreas. This focal lesion occupied virtually the whole of the pancreas. Conclusions: These three cases illustrate that focal lesions even with the same genotype (c.39929G -> A) may have a different clinical presentation and that [F-18] DOPA PET scans in very large focal lesions may be difficult to interpret. (J Clin Endocrinol Metab 97: E94-E99, 2012)