High penetrance of pheochromocytoma associated with the novel C634Y/Y791F double germline mutation in the RET protooncogene.

Context: Previous studies have shown that double RET mutations may be associated with unusual multiple endocrine neoplasia type 2 (MEN 2) phenotypes.

Objective: Our objective was to report the clinical features of patients harboring a previously unreported double mutation of the RET gene and to characterize this mutation in vitro.

Patients: Sixteen patients from four unrelated families and harboring the C634Y/Y791F double RET germline mutation were included in the study.