Gap junctions permit direct cell-to-cell passage of small cytoplasmic molecules, including ions, metabolic intermediates, and second messengers, and thereby mediate intercellular communication. Gap junction channels consist of connexin protein subunits encoded by a multigene family. Erythrokeratodermia variabilis (EKV) is an autosomal dominant disorder of keratinization characterized by migratory erythematous lesions and fixed keratotic plaques. Mutations in the GJB3 gene have been reported in some but not all families, although it has been postulated that the absence of connexin 30.3 can be compensated by other connexins.