Multiple endocrine adenomatosis type II (Sipple's syndrome) in twins.

Medullary carcinoma of the thyroid, pheochromocytoma and multiple mucosal neuromas (MEA-II), a familial disorder of neuroectodermal tissue, is believed to be inherited in an autosomal dominant pattern. The occurrence of this syndrome in twins has not previously been reported. We have documented the presence of MEA-II in a pair of twins. The high incidence of bilaterality of pheochromocytoma is emphasized, as well as the usefulness of preoperative catecholamine fractionation, and vena cava catheterization sampling.