Palmoplantar keratodermas are a group of disorders characterized by thickening of the skin on the palms of the hands and soles of the feet of affected individuals. The various forms of PPK can be divided into hereditary forms with only skin problems, hereditary syndromes with PPK as an associated feature, and acquired forms. The more commonly seen hereditary PPKs are discussed here. Hereditary forms may be localized to the hands and feet, or they may be associated with a more generalized skin disorder. Classification of hereditary PPK is frequently confusing. A simple classification incorporates 3 factors:
What causes palmoplantar keratoderma?
There are many possible causes for acquired palmoplantar keratodermas including drugs, menopause, chemicals (e.g. arsenic), mechanical stimulation, malnutrition, systemic conditions (e.g. thyroid disease, circulatory disorders), malignancies (e.g. lung cancer, colon cancer, lymphomas), skin conditions (e.g. psoriasis, eczema, pityriasis rubra pilaris, lupus erythematosus) and infectious causes (e.g. syphilis, tuberculosis, human papilloma virus).
When the condition is inherited, family members will have the same type of palmoplantar keratoderma. Autosomal dominant keratodermas are likely to affect every generation of a family. However, in autosomal recessive keratodermas parents are “carriers” of the defective gene (meaning that they don’t show the disorder on their skin) but may pass it onto their children if both parents are “carriers”. Most inherited cases of the condition are caused by a defective gene producing keratin 9.
What does palmoplantar keratoderma look like?
In diffuse palmoplantar keratoderma, the skin on the palms and or soles appears thickened and may be hard, yellowish in color. It affects the entire palm or sole.
In focal palmoplantar keratoderma, usually, only pressure or friction points are affected.
In punctate palmoplantar keratoderma, there are tiny skin spots on the palms and soles.
Transgradient palmoplantar keratoderma is rare. The condition extends onto the backs of the hands or feet.