Three RET germ-line mutations in a family with multiple endocrine neoplasia type 2A syndrome

Multiple mutations in RET proto-oncogene are not common findings in patients with multiple endocrine neoplasia type 2A syndrome (MEN2A). Screening for RET mutation in MEN2A family members is usually limited by the known affected exon. However the second unrevealed mutation in RET proto-oncogene can coexist and modify the phenotype of MEN2 patients, including age of onset of medullary thyroid carcinoma, penetrance of pheochromocytoma etc. We here describe a family with MEN 2A syndrome with combination of three different germ-line RET mutations in its members ( RET codon C634R, C634R+I852M, I852M+Y791F, Y791F). The earliest onset of medullary thyroid carcinoma was in a patient harboring the C634R+I852M double mutation at age 24 years. A 49-y.o.patient with C634R mutation has persistent medullary thyroid carcinoma after thyroidectomy at 35 years old. A carrier of Y791F mutation had no clinical evidence of disease at age of 28 years. In a child with compound I852M+Y791F mutation preventive thyroidectomy revealed C-cell hyperplasia at age of 4 years. The clinical significance of double RET mutation in the described family is not clear. Literature data of multiple germ-line RET mutations in patients with multiple endocrine neoplasia type 2A syndrome are presented.