MEN3 (previously referred to as MEN2B) is characterized by occurrence of medullary thyroid carcinoma and phaeochromocytoma in association with marfanoid habitus, pectus excavatus, medullated corneal fibers, and intestinal dysfunction with megacolon, cutaneous (including the eyelid) and mucosal neuromas also of the larynx and oral mucosa [154,155,156,157,158]. The gene discussed is RET; the disease is pheochromocytoma.