Darier and Hailey-Hailey disease: update 2021.

The autosomal-dominant genodermatoses Darier disease and Hailey-Hailey disease present special challenges to dermatologists. Despite their similar pathogenesis featuring impaired adhesion of suprabasal keratinocytes as a result of defective ATPases in epidermal calcium channels, the two diseases differ considerably in clinical presentation and therapeutic options. Darier disease is characterized by reddish brown, keratotic papules in seborrheic and intertriginous areas, which may coalesce into extensive lesions.