Involvement of the MEN1 gene locus in familial isolated hyperparathyroidism.

BACKGROUND

Familial isolated hyperparathyroidism (FIHP) is a hereditary disorder characterised by uni- or multiglandular parathyroid disease. A subset of families are likely to be genetic variants of other familial tumour syndromes in which PHPT is the main feature, for example multiple endocrine neoplasia type 1 (MEN 1) and the hyperparathyroidism-jaw tumour syndrome (HPT-JT).

OBJECTIVE

To investigate seven families diagnosed with FIHP, each with two to eight affected family members, to clarify the underlying genetic mechanism.

METHODS

The entire MEN1 gene was sequenced for germline mutations and, in addition, tumour specimens were analysed in comparative genomic hybridisation and loss of heterozygosity studies.

RESULTS

Two families exhibited MEN1 mutations, L112V and 1658delG, which were associated with loss of the wild-type 11q13 alleles in all tumours analysed. In the remaining five families, no MEN1 mutation was identified.

CONCLUSION

These results support the involvement of the MEN1 tumour suppressor gene in the pathogenesis of some of the FIHP kindreds. However, loss on chromosome 11 was seen in all tumours exhibiting somatic deletions, although in two families the tumour deletions involved 11q distal to MEN1. We conclude that the altered MEN1 gene function is of importance in the development of FIHP.