None of ten Japanese cases with S891A mutation reported in a recent study had pheochromocytoma [17], but our case report combined with previous data indicates that S891A patients as well as other MEN2A patients require early detection of subclinical pheochromocytoma to prevent a potential hypertensive crisis In MEN2 patients, the gain-of-function mutation in the RET receptor tyrosine kinase gene constitutively activates the downstream signals, leading to transformation of the cells [3]. This evidence concerns the gene NTRK1 and pheochromocytoma.