Morphometric and ultrastructural studies in an infant with leucine-sensitive hypoglycemia, hyperinsulinism and islet hyperplasia

Morphometric and ultrastructural studies were performed on biopsy material from the pancreas of an infant with severe leucine-sensitive hypoglycemia and hyperinsulinism, in whom no insulinoma had been found. Qualitatively many large B cells were observed within the pancreatic islets. Quantitatively an about two fold increase of islet tissue proportion (4.2%) was demonstrated, compared with controls of approximately the same age (1.8%). Differential islet cell counting revealed an increase in A₁ cells whereas the percentage of A₂ and B cells appeared to be unchanged. Ultrastructurally in addition to A, B, and D cells a fourth islet cell type was demonstrated in unusual frequency. Its general function and its particular significance for the hypoglycemic syndrome are unknown. The findings correspond well with recent observations on the islet cell system in cases of neonatal hypoglycemia with leucine-sensitivity and hyperinsulinism.