Epidermal nevi and epidermal nevus syndromes in pediatric practice

Epidermal nevi are hamartomas of ectodermal origin. Epidermal nevus syndromes are defined as the presence of an epidermal nevus with the involvement of other organ systems. Epidermal nevi are a manifestation of cutaneous mosaicism. Mosaicism may result from postzygotic somatic mutations. Epidermal nevi are usually located along the Blaschko’s lines. There are organoid (sebaceous nevus, comedonic nevus, eccrine nevus) and non-organoid epidermal nevus (keratinocytic epidermal nevus, inflammatory linear verrucous epidermal nevus). Epidermal nevi can be combined with extracutaneous malformations: skeletal anomalies, neurological changes, eye defects, and then it can be related with epidermal nevus syndrome. The presence in a child of large epidermal nevi and nevi located on the face and scalp requires a multidisciplinary approach involving a pediatrician, neurologist, ophthalmologist and geneticist. Currently, several well-defined epidermal nevus syndromes characterized by organoid and non-organoid (keratocytic) nevi have been described: Schimmelpenning’s syndrome, phakomatosis pigmentosa, Becker’s nevus syndrome, comedonal nevus syndrome, angora hairy nevus syndrome, Proteus’ syndrome, and CHILD syndrome (congenital hemidisplasia with ichthiosiform nevus and limb defects). Thus, follow-up of patients with epidermal nevus syndromes should be individualized and include a thorough history, clinical examination, and, if necessary, genetic testing. Typically, children with small, isolated epidermal nevus do not require further evaluation.