QUALITATIVE ANALYSIS OF RET PROTOONCOGENE MUTATIONS CAUSING THE SECOND TYPE OF MULTIPLE ENDOCRINE NEOPLASIA SYNDROME IN LITHUANIA

Abstract

Introduction.  Multiple endocrine neoplasia type 2 (MEN2) is a rare syndrome, inherited in an autosomal dominant pattern, characterized by combination of medullary thyroid carcinoma with  pheochromacytoma, tumors of the parathyroid glands and more rare tumors. Therefore, up till now there are no data about RET protooncogene mutations causing MEN2 syndrome in Lithuania. The aim of the study.  To determine and evaluate RET protooncogene mutations in patients with MEN2 syndrome in Lithuania. To determine frequency of MEN2 syndrome probands in patients with medullary thyroid carcinoma  in Lithuania. Methods. A total of 47 unrelated patients with medullary thyroid carcinoma  were enrolled into the study. Patients underwent genetic testing by DNA sequencing, detecting germline mutations causing MEN2 syndrome. Results.    RET protooncogene mutations causing MEN2 syndrome were detected in 8 patients of the 47 medullary thyroid carcinoma cases – 17.02% (CI 95% 6.4 – 27.7%). The most frequent RET protooncogene mutations (in 611 (N2), 618(N1), 634 (N2) codons) were detected to cause MEN2A syndrome (62.5%), less frequent mutation in 918 codone (N2) that caused MEN2B syndrome, most rare – familial  medullary thyroid carcinoma syndrome causative mutation in 791 codone (N1). In patients with detected MEN2 syndrome causative  mutations in RET protooncogene, medullary thyroid carcinoma manifested in younger age – 29.8 ±16.1 years, comparing with sporadic cases – 49.5±10.7 years. Conclusions. For the first time in Lithuania in unrelated patients with medullary thyroid carcinoma detected  frequency of probands and germline RET protooncogene mutations causing  MEN2 syndrome was 17.02 (CI 95% 6.4 – 27.7%). The study has also assessed the potential role of  RET protooncogene mutations to the clinical features of medullary thyroid carcinoma.