Keratinization Disorders and Genetic Aspects in Palmar and Plantar Keratodermas

Palmoplantar keratoderma (PPK) is a heterogeneous group of hereditary and acquired disorders characterized by abnormal thickening of the palms and soles. There are three clinical patterns: diffuse, focal, and punctuate. Palmoplantar keratodermas can be divided into the following functional subgroups: disturbed gene functions in structural proteins (keratins), cornified envelope (loricrin, transglutaminase), cohesion (plakophilin, desmoplakin, desmoglein 1), cell-to-cell communication (connexins) and transmembrane signal transduction (cathepsin C). Unna-Thost disease is the most common variety of hereditary PPK. Mutations in keratin 1 have been reported in Unna-Thost disease. We report 12 cases in which Unna-Thost disease was diagnosed. Genealogical study demonstrated that the genodermatosis was a familial disease inherited as an autosomal dominant disorder. Dermatological examination revealed yellowish hyperkeratosis on the palms and soles. Oral mucosa, teeth, and nails remained unchanged. Histopathological examination of the biopsy sample taken from the soles of the patients showed orthokeratotic keratosis, hypergranulosis, and acanthosis without epidermolysis.