Epidermal nevi

Published on 16/03/2015 by admin

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Epidermal nevi

Jeffrey M. Weinberg

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

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(Courtesy of Neil Fernandes, MD.)

Epidermal nevi 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 epidermal nevi have involvement of other organ systems. In these cases, the condition is termed epidermal nevus syndrome.

The most common epidermal nevi are verrucous epidermal nevi, which are best treated with an ablative procedure using either surgical or laser technology. Inflammatory epidermal nevi may respond to topical or systemic therapy.

Management strategy

The pluripotential stem cell in the embryonic ectoderm can develop into any of the cell types found within the epidermis and skin adnexae. Therefore, there are many potential nevi that may develop from these cell types. Epidermal nevi 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, the verrucous epidermal nevus is 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.

Verrucous epidermal nevi 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, epidermal nevi may be transmitted to future offspring.

There are very rare case reports of malignant change within epidermal nevi, including squamous cell carcinoma and basal cell carcinoma. The major focus of therapy is improved cosmesis. A possible role for the dermis in the development of epidermal nevi is suggested by the difficulty experienced in ablating such 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 epidermal nevi.

Epidermal nevus syndromes refer to the association of epidermal nevi 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 epidermal nevi, and the presence of any extracutaneous signs and symptoms.

Verrucous epidermal nevi

First-line therapies

image Excision under local anesthetic D
image Shave or curettage under local anesthetic D
image Cryotherapy C

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