Keratinocytic epidermal nevus in Infant/Neonate
Keratinocytic epidermal nevi are usually recognized at birth but may not become evident until later in childhood, when they present as verrucous skin-colored or hyperpigmented papules coalescing into plaques in a linear or whorled array. The degree of rugosity may vary from one patient to another and increase over time. Mutations in RAS, PIK3CA, and FGFR3 have been reported in these nevi.
Epidermolytic epidermal nevi are a subtype that, if passed on to offspring in germline fashion, yield an infant with bullous congenital ichthyosiform erythroderma eventuating in epidermolytic ichthyosis.
When epidermal nevi are associated with other cutaneous, central nervous system, skeletal, and ocular abnormalities, this is referred to as an epidermal nevus syndrome. Similar mutations are found in the syndromic forms and isolated nevus cases, the more severe presentation perhaps owing to transformation of an earlier progenitor cell yielding change in seemingly unrelated tissues. The genetic loci outlined above are also hot spots for malignancy, and there are an increasing number of reports of internal malignancy associated with extensive epidermal nevi.
Keratinocytic epidermal nevus syndrome, which features epidermal nevi, elevated fibroblast growth factor-23, and hypophosphatemia, has been found to have a genetic mosaicism with the HRAS gene in affected tissues.
D23.9 – Other benign neoplasm of skin, unspecified
239107007 – Epidermal nevus
Differential Diagnosis & Pitfalls
- Verruca vulgaris – Verrucous papules and plaques; however, they do not tend to assume a whorled pattern and do not respect the midline. If koebnerization occurs from scratching, they may appear linear.
- Linear lichen planus
- Mosaicism for ATP2A2 mutations can cause segmental Darier disease. As in epidermolytic ichthyosis, if these patients have gonadal mosaicism, offspring may have full-blown Darier disease.
- Nevus sebaceus – Papillomatous, yellow-orange, linear plaque on the scalp or face.
- Psoriasis – May present in a segmental fashion (nevoid psoriasis) but responds to topical steroids.
- Inflammatory linear verrucous epidermal nevus (ILVEN) – Congenital pruritic, linear, psoriasiform plaque.
- Lichen striatus – Presents in childhood as asymptomatic, linearly arranged, small, flat-topped, pink to skin-colored papules within the lines of Blaschko, usually on an extremity. These lesions spontaneously resolve over months to a few years and frequently leave hypopigmentation in their wake.