Linear nevus sebaceous syndrome

What causes linear nevus sebaceous syndrome?

Linear nevus sebaceous syndrome (LNSS) can be caused by a somatic mutation in any of several genes, including the HRAS , KRAS and NRAS genes. Mutations that cause LNSS occur after fertilization (they are not inherited) and are only present in some body cells (mosaicism). These three genes belong to a class of genes called oncogenes, which when mutated, have the potential to cause normal cells to become cancerous. They play important roles in cell division, cell differentiation (the process by which cells learn to do specific "jobs") and the self-destruction of cells (apoptosis).

Somatic mutations in several genes, including HRAS and KRAS, are responsible for causing isolated nevus sebaceous. It is thought that the additional signs and symptoms in people with LNSS occur because the somatic mutation affects other tissues in addition to the skin. While it is unclear exactly how mutations cause the additional symptoms of LNSS, it may relate to disrupted regulation of cell growth and division.

Last updated on 05-01-20

How is linear nevus sebaceous syndrome diagnosed?

A diagnosis of linear nevus sebaceous syndrome (LNSS) is made by identifying the characteristic symptoms, which include a sebaceous nevus along with abnormalities affecting other organ systems.

Because of the potential for multi-system involvement, anyone suspected of having LNSS should have a number of evaluations to determine the presence and extent of associated symptoms. These may include:

  • imaging studies such as CT scan or MRI of the brain (some researchers think these should be avoided unless there are signs of central nervous system involvement)
  • an electroencephalogram if epilepsy is present
  • analysis of skin biopsies
  • a complete ophthalmic (eye) exam
  • a skeletal survey
  • chests x-rays

Last updated on 05-01-20

Is linear nevus sebaceous syndrome inherited?

Linear nevus sebaceous syndrome (LNSS) is not inherited. All cases reported have been sporadic, occurring by chance in people with no family history of the condition. While LNSS is caused by genetic mutations, these mutations occur after fertilization in the affected person. They are not present in a parent's egg or sperm.

Last updated on 05-01-20

What is linear nevus sebaceous syndrome?

Linear nevus sebaceous syndrome (LNSS) is a condition characterized by the association of a large, linear sebaceous nevus (type of birthmark) with a broad range of abnormalities that may affect every organ system, including the central nervous system (CNS). The nevus usually is located on the face, scalp, or neck. The most common CNS abnormalities are intellectual disability, seizures, and hemimegalencephaly (abnormal enlargement of one side of the brain). Various other CNS abnormalities have been reported. Other signs and symptoms may include various eye abnormalities; skeletal (bone) deformities; heart defects; urogenital abnormalities; and an increased risk of cancer with age. LNSS is not inherited (it is sporadic). It can be caused by a somatic mutation in any of several genes. Mutations that cause LNSS occur after fertilization and are only present in some body cells (mosaicism). Treatment is directed towards the specific symptoms in each person.

Last updated on 05-01-20

How might linear nevus sebaceous syndrome be treated?

Treatment for linear nevus sebaceous syndrome (LNSS) is directed towards the specific symptoms and severity in each affected person. Management may require coordinated efforts of a team of specialists that may consist of pediatricians, pediatric neurologists, dermatologists, orthopedists, ophthalmologists, and other healthcare professionals.

Those who are concerned about cosmetic appearance regarding the nevus might consider surgery to remove the nevus. Surgery used to be recommended due to the risk of becoming cancerous (malignant); however, the risk of malignancy is now much less than previously believed. Surgical removal of the nevus may not always be possible due to its specific location.

Additional treatments depend on the specific abnormalities present and usually follow standard guidelines in the general population for these abnormalities. For example, epilepsy may be treated with anti-seizure medications.

Last updated on 05-01-20

Where To Start

DermNZ-Sebaceous nevus

The New Zealand Dermatolgical Society's Web site has information on nevus sebaceous, including information on linear nevus sebaceous syndrome. Click on the link above to view this information page.

Last updated on 04-27-20

Name: Nevus Outreach, Inc. 600 SE Delaware Ave., Suite 200
Bartlesville, OK, 74003, United States
Phone: +1-918-331-0595 Email: Url:
Name: Foundation for Ichthyosis and Related Skin Types FIRST 2616 North Broad Street
Colmar, PA, 18915 , United States
Phone: +1-215-997-9400 Toll Free: 1-800-545-3286 Email: Url:
Name: The Skin Cancer Foundation 149 Madison Avenue Suite 901
New York, NY, 10016 , United States
Phone: 212-725-5176 Url:
Name: Nevus Network PO Box 305
West Salem, OH, 44287,
Phone: (419) 853-4525 or (405) 377-3403 Email: Url:

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