Genetic Modifying Factors and Pheochromocytomas in Multiple Endocrine Neoplasia Type 2

Multiple endocrine neoplasia type 2A (MEN2A) is a rare syndrome associated with activating mutations in the RET proto-oncogene, combining medullary thyroid cancer in approximately 100% of cases and pheochromocytoma in 10-80% of cases. While it is accepted that the RET mutation causes variable penetrance of pheochromocytoma in the MEN2A patient population, there is no pathophysiological explanation for the phenotypic variability among patients with the same mutation, including within the same family. The aim of this study is to better characterise the genetic factors that may explain the variable penetrance of pheochromocytoma in MEN2. To this end, the investigatoes plan to perform a whole exome analysis in 2 families carrying the p. Cys634Arg mutation causing NEM2A, followed in Marseille by the principal investigator: the 1st family has 11 members all aged over 35 years, for which 8 are carriers of pheochromocytoma while 3 have not developed it (while their age is higher than the latest age of diagnosis of pheochromocytoma in this family); the 2nd family has 3 members (father and daughter with pheochromocytoma developed before 25 years; son without pheochromocytoma at an age of 42 years). The investigators believe that the analysis of these patients should allow the isolation of variants on genes potentially involved in the genesis of a pheochromocytoma in MEN2.