[Phenotypic expression of a mutation in MEN 2A documented in a family in the western part of Sweden].

A missense mutation at codon 618 of the RET proto-oncogene is a rather unusual cause of multiple endocrine neoplasia 2A. We report the phenotypic expression of this specific RET mutation in a large Swedish family. The family was mapped back to the 18th century. Since 1971 the family has been included in a biochemical screening program, and since 1994 has undergone genetic screening. Twenty-seven individuals were found to have medullary thyroid carcinoma (MTC). Eighteen were detected by screening. The incidence of pheochromocytoma (4%) and hyperparathyroidism (7%) was low. Five individuals died of MTC, but of these none had been included in the screening program. One patient underwent prophylactic thyroidectomy after positive genetic screening. MTC tumor aggressivity differed markedly between gene carriers. The screening program shows that the clinical aggressivity of MTC can be mitigated by early and adequate surgical intervention.