A NOVEL DOUBLE MUTATION VAL648ILE AND VAL804LEU OF RET PROTO-ONCOGENE IN MULTIPLE ENDOCRINE NEOPLASIA TYPE 2.

OBJECTIVE: We report the case of a female patient with multiple endocrine neoplasia type 2A (MEN2A) who was found to have a double mutation in the RET (rearranged during transfection) proto-oncogene. METHODS: RET mutational analysis was performed by Sanger DNA sequencing. RESULTS: The proband was a compound heterozygote for the RET germline mutations Val648Ile and Val804Leu on exons 11 and 14, respectively. Genetic analysis of family members showed the presence of the Val648Ile mutation in all except 1 daughter who carried the Val804Leu mutation. However, none of them showed any clinical, biochemical, or histologic signs of neoplastic disease either in the thyroid or adrenal gland. Furthermore, a daughter and the proband's sister who underwent a prophylactic thyroidectomy did not show pathologic evidence of C-cell disease. CONCLUSIONS: We hypothesize that the combined effect of the 2 mutations may have induced the development of pheochromocytoma (PHEO) in our patient. Thus, in the presence of single RET-induced mild medullary thyroid cancer (MTC) phenotype, the search for additional genetic anomalies may lead to the discovery of rare but potentially more aggressive double mutation genotypes.