[Management of multiple endocrine neoplasia syndrome type 2 families in association with rare germline mutations of the RET proto-oncogene].

INTRODUCTION: Heredity of MEN2 syndromes is caused by a heterozygous germline mutation in the RET proto-oncogene. This study describes families with rare noncysteine codon 790/791 mutations and discusses the genotype-phenotype correlation plus the therapeutic options.

PATIENTS AND METHODS: Forty-five patients with a putative sporadic MTC were screened for RET germline mutations by direct DNA sequencing. Family members of identified index cases underwent genetic analysis. Gene carriers were examined clinically and biochemicaly and underwent prophylactic thyroidectomy.

RESULTS: Five index patients were identified. In the kindreds three L790F and one Y791F carriers were detected. The thyroid gland histology of L790F carriers revealed MTC in 2 patients and C-cell hyperplasia in 2 additional patients. The Y791F carrier had a normal histology.

CONCLUSIONS: Codon 790/791 mutations had diverse penetrance: prophylactic thyreoidectomy in children is a justifiable approach for codon 790 mutation carriers, but should depend on the clinical course of codon 791 carriers.