What is an epidermal nevus?
It is a hamartoma of the epidermis, the outermost layer of the skin. A hamartoma is a malformation made up of a benign and mixed proliferation of mature cells that are arranged in a disorderly and excessive way, so it would correspond to the area where it appears.
Why do epidermal nevi appear?
Although the exact reason is unknown, it is known that there are genetic mutations that facilitate an excessive proliferation of pluripotent skin cells.
Are they very frequent?
Yes. They are present in one in every 1,000 births, although a significant percentage of epidermal nevi do not appear until childhood or adolescence, so their prevalence is higher than the one mentioned.
What do epidermal nevi look like?
These are papules or plaques (raised lesions) of orange-brown color, with a keratotic and papillomatous surface, with a tendency to group and converge. It is characteristic that they have a linear morphology following the so-called Blaschko lines (which determine the direction of migration of skin cells in embryological development). Epidermal nevi can appear only unilaterally in the body, or occupy large body areas symmetrically.
There is a variant, called linear inflammatory verrucous epidermal nevus (NEVIL) in which the nevus has a more inflammatory appearance: reddish, scaly, reminiscent of a psoriatic plaque, and which can cause itching. This variant is more common in women and usually settles unilaterally in a lower limb.
What are the health implications of epidermal nevus?
The vast majority of the time none, beyond the aesthetic alteration that they may entail. However, in epidermal nevus syndrome (Solomon syndrome) they can be associated with neurological, ocular, musculoskeletal or visceral (cardiac and genitourinary) alterations . The presence of this syndrome will be suspected when the epidermal nevi are very voluminous or generalized.
What treatments are available for epidermal nevus?
Although it is not a health problem, it is common for patients who have an epidermal nevus to look for ways to eliminate it. There are numerous therapeutic options. Topical treatments (topical or intralesional corticosteroids, calcipotriol, 5-fluorouracil, podophyllin, retinoids, chemical peels) are usually ineffective.
Definitive removal by surgical excision is effective but leaves a scar in the treated area, so aesthetically it can be a prohibitive inconvenience.
Although there are no comparative studies between the different types of lasers that can be used for removal, the most extensive publications on effectiveness point to the CO2 laser. It seems that it is the device that yields the lowest rates of recurrence of the epidermal nevus, which can be as high as 30%, especially in those lesions that are very large or of the NEVIL variant.
The clear advantages are that the procedure can be performed using topical and/or local anesthesia, that the degree of residual scar is minimal and that the recovery period after removal is very short: only superficial scabs appear in the area and the patient can lead a normal life only with strict sun protection in mind for 2-3 months.
The results of the CO2 laser are especially good in patients with epidermal nevus on the face or neck and in lesions smaller than 20 cm2. The thickness of the epidermal nevus does not seem to be related to the response or relapse rate. According to a large study, 85% of patients treated with CO2 laser report being satisfied or very satisfied with the result.
The degree of complications is minimal, with the most frequent adverse effects being temporary residual hypopigmentation and atrophic scarring if the epidermal nevus is relatively deep and requires more generous removal. This low rate of adverse effects is reduced if CO2 lasers are used in super/ultrapulsed mode (not continuous) and in the hands of an expert dermatologist.
REFERENCES
· Alonso-Castro L, Boixeda P, Reig I, de Daniel-Rodríguez C, Fleta-Asín B, Jaén-Olasolo P.Carbon dioxide laser treatment of epidermal nevi: response and long-term follow-up. Actas Dermosifiliogr. 2012 Dec; 103(10):910-8.