Close mapping of the focal non-epidermolytic palmoplantar keratoderma (PPK) locus associated with oesophageal cancer (TOC)

Focal non-epidermolytic palmoplantar keratoderma (PPK or palmoplantarectodermal dysplasia type III) is associated with oesophageal cancer inthree families: two large pedigrees located in Liverpool, UK and in themidwestern American states and one smaller family from Germany. In thesefamilies, the PPK is inherited as autosomal dominant and has a late onset,usually manifesting between 7 and 8 years of age. The disease ischaracterised by thickening of the pressure areas of the soles, but is notrestricted to the feet and also presents with oral leukokeratosis andfollicular hyperkeratosis. The disease locus [previously termed the"tylosis oesophageal cancer gene' (TOC) locus] has been mapped to17q23-qter by linkage analysis. This region is located telomeric to thekeratin 16 gene, in which mutations have been identified in focal PPKfamilies who show no increased cancer risk. We describe the close mappingof this locus to the interval between AFMb054zf9 and D17S1603 usinghaplotype analysis of additional Genethon markers in the region and showthat although the American family is unlikely to be related to either ofthe other two, the UK and German pedigrees may share a common descent. Thiswork provides a basis for positional cloning and candidate gene analysis inorder to identify a gene that may be involved in familial oesophagealcancer.