There is an increased risk of hair follicle tumours and rarely skin cancers arising in naevus sebaceous in older children.
Large epidermal naevi may sometimes be associated with malformations in the brain, eyes or bones. The name epidermal naevus syndrome is then used. Rarely bone involvement may result in hypophosphatemic rickets.
EN can be part of other syndromes such as Proteus syndrome.
As the mutation is in the fetal tissue not the parents’ sperm or egg, usually there is no risk of having another child with this birthmark. However, there are some situations where the child with the birthmark may be able to pass on the mutation to their offspring. This to date has been reported in some subtypes of EN including epidermolytic EN (keratin 1, 10), linear Darier’s (ATP2A2), porokeratotic eccrine naevus (GJB2). This is best discussed with a geneticist. A skin biopsy may help classify some of these types.