Phenotype mapping of the multiple endocrine neoplasia type II syndrome.

The multiple endocrine neoplasia (MEN) IIb syndrome has been differentiated from MEN IIa by the presence of various phenotypic characteristics such as mucosal neuromas, marfanoid habitus, congenital skeletal anomalies, and prominent corneal nerves, as well as the lack of parathyroid involvement. Analysis of a kindred with some characteristics of both syndromes (including an associated chromosomal deletion) tends to unify the MEN II syndromes as a single disorder with variable expressivity. The linear map of the genetic determinants is postulated to conform with the following phenotype order: parathyroid tumors, medullary thyroid cancer, pheochromocytomas, skeletal changes, prominent corneal nerves, mucosal neuromas, and marfanoid habitus. Appreciation of this sequence can allow earlier identification and treatment of affected individuals.