RET oncogene mutations in a large Korean kindred with familial medullary thyroid carcinoma

6066 Background: Familial medullary thyroid carcinoma (FMTC) is related to germ-line mutations in the RET proto-oncogene. The mutations concern mainly cystein residues in exons 10 and 11, whereas noncystein mutations in exons 13–16 are rare. These mutations have been recorded in the different populations, but to date there is no corresponding study in Korean families. In this study, we identify the RET mutations in the Korean family with FMTC and propose therapeutic approach in managing the disorder. Methods: The large family consists of 4 generations with a total of 32 individuals. There was a history of MTC in five members of the family. The index case was a 67-yr- old woman who underwent total thyroidectomy and both modified radical neck dissection in our hospital at the age of 48. We analysed exons 10, 11, 13, 14, 15 and 16 in index patients using DNA sequencing. Twenty-nine subjects from the family were clinically assessed and subsequently molecularly analysed for the presence of RET gene mutations. Results: We have found a missense TGC?AGC mutation at codon 618 in Exon 10. This transversion leads to the substitution of cystein with serin. The mutation was detected in all five MTC patients as well as in 6 asymptomatic relatives. The mutation shows a wide clinical heterogenecity, as there are carrier patients with age of diagnosis ranging from 9 to 64 years. Conclusions: It is likely that the mutation causes FMTC, because no other mutation was found in RET. This study showed 100% accordance between presence of the disease and gene carrier status is reported. Total preventive thyroidectomy has been recommended in all carriers of RET genetic defects. No significant financial relationships to disclose.