Clinical presentations and RET protooncogene mutations in seven multiple endocrine neoplasia type 2 kindreds.

BACKGROUND

Multiple endocrine neoplasia type 2 (MEN 2) is a group of related autosomal dominant cancer syndromes caused by mutations in the RET protooncogene. A subset of familial Hirschsprung's disease, aganglionic megacolon, is also caused by mutations in this gene.

METHODS

The authors performed mutation analysis of exons 10, 11, 13, and 16 of the RET gene is six established MTN 2 kindreds and in six patients with apparent sporadic disease, in order to correlate their genotypes and phenotypes.

RESULTS

One of these kindred's carried both Hirschsprung's disease and MEN 2A in conjunction with a cysteine-to-arginine substitution of codon 620 of the RET gene. One patient with apparently sporadic disease was found to have a germline M918T mutation. Patients with confirmed familial disease all carried pathologic germline mutations of RET.

CONCLUSIONS

Several lines of evidence support a gain of function mechanism for tumorigenesis in the MEN 2 syndromes but a loss of function mechanism for aganglionosis in Hirschsprung's disease. The authors propose that a multihit mechanism can reconcile the apparent paradox of a single mutation that gives rise to both gain and loss of function disorders in a single patient.