Characterization of the largest kindred with MEN2A due to a Cys609Ser RET mutation.

RET codon 609 point mutations are rare and may predispose to aggressive medullary thyroid carcinoma (MTC). In a kindred with 15 carriers of the Cys609Ser RET mutation we observed no MTC before 17 years of age, no lymph node metastases before 30 years and no distant metastases before 60 years. Two patients developed pheochromocytoma and one had primary hyperparathyroidism as the first sign of the syndrome. In conclusion, at variance from what already known, in this large kindred the Cys609Ser RET mutation predispose to a scarcely aggressive, highly penetrant MTC and a low penetrance of pheochromocytoma and primary hyperparathyroidism.