[Acanthokeratolytic epidermal nevus: acanthokeratolysis is hereditary, not the nevus]

Epidermal naevus of the acanthokeratolytic (epidermolytic) type is a mosaic birth defect. The underlying mutation may also be present in the gonads and can then be transmitted to the next generation. The affected child, however, will always show a diffuse involvement of the entire body in the form of bullous congenital ichthyosiform erythroderma. In other words, the phenotype can be transmitted, but not the mosaic. This explains why acanthokeratolytic epidermal naevus always affects the parent and never the child when it is observed in a family together with bullous congenital ichthyosiform erythroderma.