What is epidermal nevus?
An epidermal nevus (plural: nevi) is an abnormal, noncancerous (benign) patch of skin caused by an overgrowth of skin cells. Epidermal nevi are typically seen at birth or develop in early childhood. They can be flat, tan patches of skin or raised, velvety patches. As the affected individual ages, the nevus can become thicker and darker and develop a wart-like (verrucous) appearance. Often, epidermal nevi follow a pattern on the skin known as the lines of Blaschko. The lines of Blaschko, which are invisible on skin, are thought to follow the paths along which cells migrate as the skin develops before birth.
There are several types of epidermal nevi that are defined in part by the type of skin cell involved. The epidermis is the outermost layer of skin and is composed primarily of a specific cell type called a keratinocyte. One group of epidermal nevi, called keratinocytic or nonorganoid epidermal nevi, includes nevi that involve only keratinocytes. Other types of epidermal nevi involve additional types of epidermal cells, such as the cells that make up the hair follicles or the sebaceous glands (glands in the skin that produce a substance that protects the skin and hair). These nevi comprise a group called organoid epidermal nevi.
Some affected individuals have only an epidermal nevus and no other abnormalities. However, sometimes people with an epidermal nevus also have problems in other body systems, such as the brain, eyes, or bones. In these cases, the affected individual has a condition called an epidermal nevus syndrome. There are several different epidermal nevus syndromes characterized by the type of epidermal nevus involved.
How common is epidermal nevus?
Epidermal nevi affect approximately 1 in 1,000 people.
What genes are related to epidermal nevus?
Mutations in the FGFR3 gene have been found in approximately 30 percent of people with a type of nevus in the keratinocytic epidermal nevi group. The gene mutations involved in most epidermal nevi are unknown.
Mutations associated with an epidermal nevus are present only in the cells of the nevus, not in the normal skin cells surrounding it. Because the mutation is found in some of the body’s cells but not in others, people with an epidermal nevus are said to be mosaic for the mutation.
The FGFR3 gene provides instructions for the fibroblast growth factor receptor 3 (FGFR3) protein. This protein is involved in several important cellular processes, including regulation of growth and division of skin cells. The FGFR3 protein interacts with specific growth factors outside the cell to receive signals that control growth and development. When these growth factors attach to the FGFR3 protein, the protein is turned on (activated), which triggers a cascade of chemical reactions inside the cell that control growth and other cellular functions.
The most common FGFR3 gene mutation in epidermal nevi creates a protein that is turned on without attachment of a growth factor, which means that the FGFR3 protein is constantly active. Cells with a mutated FGFR3 gene grow and divide more than normal cells. In addition, these mutated cells do not undergo a form of self-destruction called apoptosis as readily as normal cells. These effects result in overgrowth of skin cells, leading to epidermal nevi.
Read more about the FGFR3 gene.
How do people inherit epidermal nevus?
This condition is generally not inherited but arises from mutations in the body’s cells that occur after conception. This alteration is called a somatic mutation.
Occasionally, the somatic mutation occurs in a person’s reproductive cells (sperm or eggs) and is passed to the next generation. An inherited FGFR3 gene mutation is found in every cell in the body, which results in skeletal abnormalities rather than epidermal nevus.
Complications of epidermal naevi
Most epidermal naevi remain unchanged in adulthood and do not cause any problems. However, very rarely another tumour can arise within the lesion. This may be a harmless syringocystadenoma papilliferum, or a skin cancer.
Therefore, if a lump or sore appears within an epidermal naevus, arrange for it to be reviewed by your dermatologist. It may require a biopsy or cutting out.
Treatment of epidermal naevi
There is no real effective medical treatment for epidermal naevi. Topicals may reduce the wartiness in some cases. If necessary, laser or surgical removal of naevi may be performed.
Epidermal Nevus Syndromes
Epidermal nevus syndromes (ENSs) are a group of rare complex disorders characterized by the presence of skin lesions known as epidermal nevi associated with additional extra-cutaneous abnormalities, most often affecting the brain, eye and skeletal systems. Epidermal nevi are overgrowths of structures and tissue of the epidermis, the outermost layer of the skin. The different types of epidermal nevi can vary in size, number, location, distribution and appearance. Neurological abnormalities that can be associated with ENSs can include seizures, cognitive impairment, developmental delays and paralysis of one side of the body (hemiparesis). Skeletal abnormalities can include abnormal curvature of the spine, malformation of the hip and abnormalities of the arms and legs (e.g., underdevelopment or absence or overgrowth of limbs). Ocular abnormalities may include cataracts, clouding (opacity) of the cornea or partial absence of tissue of the iris or retina (colobomas). Endocrine abnormalities such as vitamin D-resistant rickets have been associated with Schimmelpenning syndrome. The specific symptoms and severity of ENSs can vary greatly from one person to another. Most ENSs occur randomly for no apparent reason (sporadically), most likely due to a gene mutation that occurs after fertilization (postzygotic mutation) and is present in only some of the cells of the body (mosaic pattern).
Wilms’ tumor is a rare kidney cancer that primarily affects children. Also known as nephroblastoma, Wilms’ tumor is the most common cancer of the kidneys in children. Wilms’ tumor most often affects children ages 3 to 4 and becomes much less common after age 5.
Wilms’ tumor most often occurs in just one kidney, though it can sometimes be found in both kidneys at the same time.
Improvements in the diagnosis and treatment of Wilms’ tumor have improved the prognosis for children with this disease. The outlook for most children with Wilms’ tumor is very good.
It’s not clear what causes Wilms’ tumor.
Doctors know that cancer begins when cells develop errors in their DNA. The errors allow the cells to grow and divide uncontrollably and to go on living when other cells would die. The accumulating cells form a tumor. In Wilms’ tumor, this process occurs in the kidney cells.
In a small number of cases, the errors in DNA that lead to Wilms’ tumor are passed from parents to children. In most cases, there is no known connection between parents and children that may lead to cancer.
May Be Caused by
- Aniridia-Wilms tumor association
- Asplenia with liver malformation
- Beckwith-Wiedemann syndrome
- Bloom syndrome
- Brachmann-de Lange syndrome
- Chromosome 15q deletion
- Congenital heart disease
- Congenital obstructive uropathy-renal hamartoma-nephroblastomatosis
- Epidermal nevus syndrome
- Familial Wilms tumor
- Frasier syndrome
- Hereditary multiple exostoses
- Horseshoe kidney
- Hyperparathyroidism-jaw tumor syndrome
- Klippel-Trénaunay-Weber syndrome
- Li-Fraumeni syndrome
- Male pseudohermaphroditism
- Neurofibromatosis type 1
- Parkes Weber syndrome
- Perlman syndrome
- Pleuropulmonary blastoma-Wilms tumor association
- Poland syndrome
- Prader-Willi syndrome
- Premature chromatid separation
- Robin sequence
- Silver-Russell syndrome
- Simpson-Golabi-Behmel syndrome
- Trisomy 13
- Trisomy 18
- WAGR syndrome
- Wilms tumor-hyponatremic/hypertension syndrome
- Wilms tumor-multiple lung hamartomas