Genetic linkage studies in non-epidermolytic palmoplantar keratoderma: evidence for heterogeneity.

The palmoplantar keratodermas (PPK) are a group of skin diseases characterized by thickening of the skin of the palms and soles due to abnormal keratinization. We have performed linkage analysis on families affected with three distinct forms of non-epidermolytic PPK (NEPPK): focal, diffuse and punctate. Genetic heterogeneity was demonstrated, with focal NEPPK linked to the region on chromosome 17 harbouring the type I keratin cluster, diffuse NEPPK linked to the region on chromosome 12 containing the type II keratin cluster, and in the punctate NEPPK pedigrees, linkage was excluded to both of these keratin clusters. This study provides evidence for genetic differences between these forms of NEPPK and also between NEPPK and epidermolytic PPK (EPPK) in which mutations in keratin 9 have been demonstrated.