Hereditary palmoplantar keratodermas. Part II: syndromic palmoplantar keratodermas - Diagnostic algorithm and principles of therapy.

Hereditary palmoplantar keratodermas (PPKs) comprise a large and heterogeneous group of disorders characterized by persistent thickening of the epidermis at palmar and plantar surfaces. Clinical and genetic features of isolated and complex PPKs have been reviewed in part I of this 2-part review. Here we focus on clinical and molecular classification of syndromic PPKs which are recognized by additional extracutaneous manifestations, in particular deafness, specific mucosal lesions, cardiomyopathy, inborn errors of metabolism, involvement of internal organs or disorders of sexual development. Other genetic diseases, which may show palmoplantar involvement, such as selected subtypes of hereditary epidermolysis bullosa, various hereditary ichthyoses and other keratinization disorders, several ectodermal dysplasias and some multisystem genetic disorders, are also briefly summarized. PPK diagnosis is based on inheritance pattern, age at onset, morphology, distribution and severity of hyperkeratosis, pattern of additional dermatological and systemic manifestations and laboratory findings. Molecular analysis is at present the gold standard to confirm the diagnosis in PPK forms due to mutations in known causative genes. No specific and curative therapy is currently available for PPKs which highly impair patients' quality of life. Topical treatments are symptomatic and offer only temporary relief. Among systemic treatments, retinoids improve disease symptoms in the majority of patients.