Hyperinsulinemic hypoglycemia in adults with islet-cell hyperplasia and degranulation of exocrine cells of the pancreas

Five adults with pancreatic islet-cell hyperplasia presenting as hyperinsulinemic hypoglycemia are reported. Additional lesions including nesidioblastosis, adenomatosis, and insulinoma were variably present. This apparent spectrum of islet-cell lesions has been rarely noticed in hypoglycemic adults, although it is a recognized cause of a similar clinical syndrome in children. B-cell hyperplasia was confirmed in all five cases by histochemistry, immunochemistry, and electron microscopy. In addition, nodules of eosinophilic exocrine cells, another recently recognized finding in similar cases, were present in all cases studied. Ultrastructural study revealed that these nodules were composed of degranulated acinar cells. These acinar changes may provide a diagnostic aid in cases of pancreatic endocrine hyperplasia. Consideration of the embryologic development of the pancreas suggests that this spectrum of islet-cell hyperplasia and acinar cell change is due to neoformation of islets from ducts. The etiologic factors of such proliferation are still unknown.