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Epidermal nevi
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Epidermal nevi (EN; OMIM162900) are congenital hamartomas of embryonal ectodermal origin classified on the basis of their major component. The components may be sebaceous, apocrine, eccrine, follicular, or keratinocytic. An estimated one-third of individuals with EN have involvement of other organ systems. In these cases, the condition is termed epidermal nevus syndrome .
The most common EN are verrucous epidermal nevi (VEN), which are best treated with an ablative procedure using either surgical or laser technology. Inflammatory EN may respond to topical or systemic therapy.
The pluripotential stem cell in the embryonic ectoderm can develop into any of the cell types found within the epidermis and skin adnexa. Therefore many potential nevi may develop from these cell types. EN may be classified according to the predominant cell type. However, there may be different cell populations or overlap between different areas within the same nevus.
The focus of this chapter will be on nevi derived from keratinocytes. Of these, VEN are the most common. Other forms include an inflammatory linear verrucous epidermal nevus (ILVEN), an acantholytic or Darier-like nevus, an epidermolytic form, and linear porokeratosis. Very rarely an epidermal nevus may be associated with other birth defects, and a number of epidermal nevus syndromes have been described.
VEN may be localized, segmental, and rarely systematized. The individual lesions are verrucous papules, which may be pink, brown, or gray. These may develop as a result of mosaicism, and, if there is gonadal mosaicism, EN may be transmitted to future offspring.
There are very rare case reports of malignant change within EN, including squamous cell carcinoma and basal cell carcinoma.
Management Strategy
The major focus of therapy is improved cosmesis. A possible role for the dermis in the development of EN is suggested by the difficulty experienced in ablating these lesions surgically without destroying the underlying dermis. Surgical management of these lesions presents challenges. Superficial treatments, which remove only the epidermis, have a high recurrence rate, whereas excision or more aggressive ablative procedures may produce unacceptable scarring. Laser technology provides the surgeon with more precise tools to maximize efficacy while minimizing scarring. Alternatively, for very widespread lesions, a variety of topical regimens, as well as systemic retinoids, have been reported to produce some benefit.
ILVEN presents in early childhood as a pruritic, erythematous, linear plaque. It shares many features with psoriasis, and certain cases respond to antipsoriatic therapies such as topical vitamin D analogs, corticosteroids , and dithranol . This has led some authors to suggest that this condition is a nevoid form of psoriasis. Epidermolytic and acantholytic nevi are more likely to respond to treatment with retinoids .
Specific Investigations
An epidermal nevus can most often be diagnosed solely on the clinical presentation and distribution of the lesion. A skin biopsy can be used both to confirm the diagnosis if necessary and to determine the predominant cell type and the presence of inflammatory changes, acantholysis, or dysplasia. This can be helpful in determining which therapeutic modality is most likely to succeed. If histopathology demonstrates an epidermolytic nevus, the individual should be counseled that there is a possibility that the mutation could be transmitted to offspring, with the risk that their children may have generalized cutaneous involvement. Biopsy can also indicate the rare occurrence of squamous or basal cell carcinoma, which can develop in EN.
Epidermal nevus syndromes refer to the association of EN with extracutaneous manifestations involving the central nervous system, eyes, or bones. The evaluation for systemic involvement should be based on the clinical extent of the EN and the presence of any extracutaneous signs and symptoms.
Generalized epidermolytic hyperkeratosis in two unrelated children from parents with localized linear form, and prenatal diagnosis
Chassaing N, Kanitakis J, Sportich S, et al. J Invest Dermatol 2006; 126: 2715–7.
The authors report two unrelated children with epidermolytic hyperkeratosis, both born to a parent affected with epidermolytic epidermal nevi (EEN); prenatal diagnosis in two successive pregnancies of one of the patients with EEN is described.
Squamous cell carcinoma arising in a verrucous epidermal naevus
Ichikawa T, Saiki M, Kaneko M, et al. Dermatology 1996; 193: 135–8.
A case report of a squamous cell carcinoma arising in a 74-year-old man with an epidermal nevus, plus a review of the literature, which revealed 18 previous reports of malignant change in EN.
Basal cell carcinoma developing in verrucous epidermal nevus
De D, Kanwar AJ, Radotra BD. Indian J Dermatol Venereol Leprol 2007; 73: 127–8.
A 58-year-old farmer with a hyperpigmented, soft verrucous plaque on the right temporoparietal region since birth presented with an ulcer of 8 months’ duration. A diagnosis of basal cell carcinoma (BCC) arising in a verrucous epidermal nevus was made. Biopsy was consistent with BCC.
Epidermal nevus syndromes: new insights into whorls and swirls
Asch S, Sugarman JL. Pediatr Dermatol 2018; 35 :21–9.
The authors review recent genetic discoveries involving EN, including nevus sebaceous, keratinocytic epidermal nevus, nevus comedonicus, congenital hemidysplasia with ichthyosiform nevus and limb defects syndrome, phakomatosis pigmentokeratotica, Becker nevus, porokeratotic adnexal ostial nevus, ILVEN, and cutaneous-skeletal hypophosphatemia syndrome. Several mutations have been identified in EN, including mutations in Ras, fibroblast growth factor receptor 3 (FGFR3), phosphatidylinositol‐4,5‐bisphosphate 3‐kinase catalytic subunit alpha (PIK3CA), and keratins.
Epidermal nevus syndromes: clinical findings in 35 patients
Vidaurri-de la Cruz H, Tamayo-Sanchez L, Duran-McKinster C, et al. Pediatr Dermatol 2004; 21: 432–9.
Of patients with EN, 10%–18% may have disorders of the eye and skeletal and nervous systems.
Does inflammatory linear verrucous epidermal nevus represent a segmental type 1/type 2 mosaic of psoriasis?
Hofer T. Dermatology 2006; 212: 103–7.
The author hypothesizes that inflammatory linear verrucous eruption besides nevoid psoriasis/linear psoriasis represents a further segmental type 1/type 2 mosaic of psoriasis, which, if a (verrucous) epidermal nevus exists, shows a high affinity of occurrence in close context to such a nevus. Heritability is thought to be possible.
Papular epidermal nevus with skyline basal cell layer (PENS): three new cases and review of the literature
Luna PC, Pannizardi AA, Martin CI, et al. Pediatr Dermatol 2016; 33: 296–300.
Papular epidermal nevus with skyline basal cell layer (PENS) is a recently described type of epidermal nevus with characteristic histopathologic findings. The authors note that cases of Blaschkoid distribution, associated extracutaneous manifestations, and familial cases have been reported. The probability of having extracutaneous manifestations is 6.3 times greater in those with more than four lesions. Therefore these patients require closer follow-up.
Verrucous Epidermal Nevi
First-Line Therapies
Epidermal nevus: surgical treatment by partial-thickness skin excision
Dellon AL, Luethke R, Wong L, et al. Ann Plast Surg 1992; 28: 292–6.
A case report of treatment of a systematized epidermal nevus by partial-thickness skin excision. This cleared the nevus but led to extensive hypertrophic and keloidal scarring.
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