What are the other Names for this Condition? (Also known as/Synonyms)

• EN (Epidermal Nevus)
• Epidermal Naevus

What is Epidermal Nevus? (Definition/Background Information)

• An Epidermal Nevus (EN) is a benign, yellowish-brown, wart-like skin lesion, which is commonly present at birth, or develop during childhood 
• The skin lesions may appear as plaques (abnormal ‘flat’ patches) or as papules (small, raised skin forms), and are usually present in the trunk or the extremities  
• EN may be localized to a small fraction of total body surface area, but can also cover a vast extent of skin, causing significant cosmetic problems
• EN has also been associated with a number of atypical (unusual) presentations, such as involving the maxilla (upper jaw), lesions found on the palms, or even an adult onset/presentation
• Sometimes, EN lesions do not involve only the skin. They may be present as a part of Epidermal Nevus Syndrome, in which there is involvement of other areas of the body such as blood vessels, kidneys, bone, brain, eyes, etc.  

Epidermal Nevus can present itself in three ways. They are specifically named, based on the differences, in the way they appear:

• Nevus verrucosus - usually presents as single lesions, or as multiple but localized lesions
• Nevus unius lateris – may be present as lesions arranged in a linear pattern
• Ichthyosis hystrix - has a more generalized manifestation

Each of these EN subtypes is clinically similar and the lesion biopsies, when examined by a pathologist on microscope slides, look the same.

Who gets Epidermal Nevus? (Age and Sex Distribution)

• Epidermal Nevus affects 1 in 1000 individuals; most cases occur without any genetic basis (they are sporadic)
• It is seen to occur with equal frequency, in both males and females
• There is also an equal distribution of EN lesion bearers, across different races and ethnic background

What are the Risk Factors for Epidermal Nevus? (Predisposing Factors)

The possible risk factors for Epidermal Nevus include:

• Epidermal Nevus can have a genetic involvement, though it is not very common. In such cases, it has an autosomal dominant pattern of manifestation
• The risk factors for EN are not yet completely understood. However, cell DNA mutations are thought to play to a role. Studies have implicated mutations in fibroblast growth factor receptor 3 genes (FGFR 3) as a definitive risk factor for the development of the keratinocytic type (skin-cell type) of Epidermal Nevi

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Epidermal Nevus? (Etiology)

• The majority of Epidermal Nevi (plural of Nevus) are sporadic, i.e. they occur after birth, without a genetic basis. Example: An individual, who is said to have a sporadic keratinocytic Epidermal Nevus, would be someone, who developed a FGFR 3 mutation after birth. Such formations are also referred to as mosaics, because the mutations are only seen in the affected lesion cells and not in other cells of the body
• The FGFR 3 mutation is seen in about 30% of keratinocytic Epidermal Nevi cases; and the other cells of the body without this lesion, do not have this mutation
• Normally, FGFR 3 is found on the surface of cells. Its function is to promote skin cell growth and development after being bound by a signal, outside of the cell. In those individuals with mutated form of FGFR 3, the receptor is activated by itself, without the external signal. As a result, cells continue to grow abnormally causing the nevus. These mutated cells have also been observed, as not obeying the rules of apoptosis (a programmed cell death), which are typically regulated by skin processes
• When there is a genetic inheritance to EN, the mutations responsible for the lesions, occur in the sex cells of the parents. The inheritors of such mutations usually have extensive disease, typically Epidermal Nevus Syndromes

What are the Signs and Symptoms of Epidermal Nevus?

The signs and symptoms of Epidermal Nevus include:

• They are benign, wart-like lesions found on the skin, which usually begin during childhood
• Epidermal Nevus can be present as Epidermal Nevus Syndrome; meaning that there is involvement of other body areas, such as blood vessels, kidneys, bone, brain, eyes, etc.
• Individuals with EN, also often have other skin lesions, such as café-au-lait macules (pigmented birthmarks), vascular abnormalities, and melanocytic or hypopigmented (lacking skin color) skin lesions that are congenital

How is Epidermal Nevus Diagnosed?

A diagnosis of Epidermal Nevus is established by:

• Complete physical examination with a thorough medical history
• A biopsy of Epidermal Nevus, reveals that the skin abnormality is limited to the epidermal (outermost) layer of skin

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Epidermal Nevus?

Complications due to Epidermal Nevus are rare; but, it is observed that there is an association with the development of basal cell carcinoma, squamous cell carcinoma, keratoacanthoma, and clear cell acanthoma.

How is Epidermal Nevus Treated?

• There is generally no treatment required for Epidermal Nevus, which is a benign skin lesion. Whenever treatment is employed, it is mainly due to cosmetic reasons, or to prevent or reduce the risk of infection with lesions found in areas of increased friction, such as groin and armpits
• Localized EN lesions may be treated with topically applied steroids or tretinoin cream. Oral retinoids may be attempted for generalized presentations. Such treatments do not completely resolve the problem, but mostly reduce the severity of these lesions
• Surgical excision, dermabrasion, cryosurgery, electrosurgery, and laser surgery, have all been used in removing EN. Surgical removal has proven to be the most successful treatment method; though, it is associated with certain risks

How can Epidermal Nevus be Prevented?

Currently, there are no known means of preventing Epidermal Nevi occurrence.

What is the Prognosis of Epidermal Nevus? (Outcomes/Resolutions)

• The prognosis of Epidermal Nevus is good, especially with a surgical approach. However, there have been incidences of lesion recurrence, even after surgical treatment measures, such as dermabrasion and cryosurgery
• However, Epidermal Nevus Syndrome is much more difficult to treat to a complete resolution, due to manifestations found in internal organs

Additional and Relevant Useful Information for Epidermal Nevus:

• Sometimes, Epidermal Nevi may involve only the keratinocytes (cells on the outermost layer of skin). Such EN groups are termed keratinocytic or nonorganoid Epidermal Nevi
• EN is also known to involve cells that surround hair follicles or sebaceous glands (glands that secrete sebum, a substance that moisturizes the skin, hair, and hair follicles). These are referred to as organoid Epidermal Nevi
• Epidermal Nevi is known to be associated with keratitis-ichthyosis-deafness, Gardner’s syndrome, Rubinstein-Taybi syndrome, and many others
• EN is diagnosed by pathologist after examining microscope slides of skin biopsy for the presence of increase in keratinization of epidermal cells (when cells in the epidermis becomes hardened with hair-like, or nail-like, or calloused, consistency), increase in cell number, growth of underlying cells, and pigmentation (papillomatosis and acanthosis), and increased invasion of rete ridges (demarcation at the end of epidermis, which normally form ridges in the dermal layer of skin)
• The microscope slides of EN, as described above, are very similar to nigricans acanthosis and seborrheic keratosis, which are also benign skins lesions. Hence, it is important for the healthcare provider to give a good clinical history to the pathologist