Costello syndrome with pancreatic islet cell hyperplasia.

A 3-month-old boy with Costello syndrome (CS) developed respiratory distress and fatal arrhythmias. An autopsy showed cardiac hypertrophy, mild coarctation of the aorta, and pancreatic islet cell hyperplasia. To our knowledge, this is the first report of a pancreatic abnormality in CS. Islet cell hyperplasia has also been observed in leprechaunism, Beckwith-Wiedemann (BWS), and Simpson-Golabi-Behmel syndromes. The syndromes are thought to involve abnormal insulin or insulin-like growth factor (IGF) pathways. Clinical similarities among these disorders and CS, together with the finding of islet cell hyperplasia, suggest that they may be related.