Multiple endocrine neoplasia syndromes, children, Hirschsprung's disease and RET.

Multiple endocrine neoplasia (MEN) type 2 syndromes are autosomal dominant clinical associations characterized by a common clinical feature, medullary thyroid carcinoma (MTC). The ability to accurately predict the risk by genetic RET proto-oncogene analysis has resulted in the active follow-up of children at risk for developing early metastatic tumours and which can be prevented by prophylactic thyroidectomy. The C634 and M918T mutations (associated with MEN2A and MEN2B, respectively) are particularly associated with early aggressive behavior and distant metastatic spread requiring early intervention. RET is known to be involved in cellular signalling processes during development and controls the survival, proliferation, differentiation and migration of the enteric nervous system (ENS) progenitor cells, as well as the survival and regeneration of sympathetic neural and kidney cells. The centrality of RET in the etiology of both MEN2 and HSCR is now well established with fairly consistent associations existing between RET genotype and phenotype in MEN2. The relationship between Hirschsprung's disease (HSCR) MEN2 syndromes appears to be a highly significant one, sharing a common etiological factor in the RET proto-oncogene. It is now well accepted that most HSCR arises from loss of function, RET mutations, RET haploinsufficiency or RET polymorphisms and haplotypes of the RET promotor region. MEN2 syndromes result from gene up regulation due to germline activating mutations in the RET proto-oncogene (1:500,000). MTC is mostly associated with variations in the 5 cysteine RET radicals and codon-risk management protocols are of considerable value but not infallible. Oncogenic RET mutations may, however, vary between specific population groups. RET analysis in MEN has revolutionized the management of children of MEN2 and allowed surgical prediction and prophylaxis to take place. We discuss the role of genetic testing and possible guidelines for the management of patients from MTC families. The future appears full of promise and the current evaluation of RET-targeting tyrosine kinase and other inhibitors are of considerable interest in the management of these conditions.