Of the 33 MEN2 patients, 32 (97% [20 symptomatic patients including 9 index-cases and 11 clinical patients, and 12 asymptomatic carriers]) who were diagnosed with MTC or C-cell hyperplasia (CCH) clinically or based on pathologic evaluation, the mean diagnostic age was 34.6 ± 16.1 years; 1 RET-carrier (F8-III5) had no abnormalities. This evidence concerns the gene RET and medullary thyroid gland carcinoma.