[From gene to disease; from the RET gene to multiple endocrine neoplasia types 2A and 2B, sporadic and familial medullary thyroid carcinoma, Hirschsprung disease and papillary thyroid carcinoma].

The RET gene encodes a receptor tyrosine kinase involved in normal and neoplastic development of neural crest cell lineages. Activating RET mutations are present in patients with multiple endocrine neoplasia types 2A and 2B (MEN2A, 2B) and in familial medullary thyroid carcinoma (FMTC) patients, whereas inactivating RET mutations are found in patients with Hirschsprung (HSCR) disease. In particular for MEN2A and FMTC, the clinical management largely depends on the specific mutation found.