Multiple endocrine neoplasia type IIA (https://omim.org/entry/171400) is an autosomal dominant syndrome of multiple endocrine neoplasms, including medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid adenomas. MEN2B (162300), characterized by MTC with or without pheochromocytoma and with characteristic clinical abnormalities such as ganglioneuromas of the lips, tongue and colon, but without hyperparathyroidism, is also caused by mutation in the RET gene (summary by Lore et al., 2001).
For a discussion of genetic heterogeneity of multiple endocrine neoplasia, see MEN1 (131100).