What is a nevus sebaceous?
A nevus sebaceous is a rare type of birthmark that can be found on the face, neck, forehead, or scalp. While it can appear anywhere on the head, it most often occurs on the scalp. Though it’s technically classified as a hair follicle tumor and is associated with other conditions, a nevus sebaceous is benign.
A diagnosis of nevus sebaceous is also sometimes referred to as “Jadassohn Disease II” or “organoid nevus.”
Nevi sebaceous present differently in young children than in adulthood, though at all stages of life the lesions are hairless.
In young children and infants
A nevus sebaceous will appear as a yellow-orange patch of skin that is hairless and smooth. It’s circumscribed, meaning that it has well-defined borders, and is likely to appear either oval or linear in shape. Typically, there will be just one patch of skin affected, and it may look like a plaque.
It’s common for the lesion to change during puberty due to hormonal fluctuations. In some cases, this is when the lesion will be diagnosed, as it starts to change in appearance.
As a person matures, the epidermis thickens and the lesion presents differently. It often becomes more pronounced, and either becomes more bumpy or scaly. Some compare the appearance of the nevi to a patch of thick warts. The nevi may also grow in size as a child moves through adolescence.
Nevi sebaceous have only cosmetic symptoms. They don’t itch or cause pain, unless secondary complications arise like sores.
There’s typically only one lesion present, and it usually presents on the scalp. In rare cases, there may be multiple lesions. It’s also possible for the lesion to appear on the face, neck, or forehead instead of, or in addition to, the scalp.
Sometimes nevi sebaceous are accompanied by linear nevus sebaceous syndrome. This is a very rare condition that can cause:
- intellectual disability
- hemimegalencephaly, enlargement of one side of the brain
A nevus sebaceous is a congenital malformation. It comes from a defect that occurs before birth in the outer layer of the embryo called the ectoderm. The ectoderm is responsible for development of both neural tissue and the epidermis. In cases of nevi sebaceous, the epidermis becomes abnormally thicker over time.
As with most other conditions relating to nevi, it’s thought that a nevus sebaceous may be caused by a genetic condition. This seems to be supported by findings that those with a family history of the condition are at higher risk for being born with it, or passing it along to their children. That being said, cases are also highly sporadic, meaning that an individual is affected without prior family history.
A mutation in the PTCH gene has been linked with the development of nevus sebaceous. Since mutations in the PTCH-1 gene
Aside from family history as an increased risk factor, this condition occurs fairly equally among all demographics. Both women and men are affected equally, and no race or ethnicity is more or less likely to develop it.
Because all nevi sebaceous are present at birth, it’s common for someone to be diagnosed during infancy or childhood. In many cases, either the parents or doctor will notice it then.
Your doctor may be able to diagnose this condition just from a physical exam and asking about your medical history. They may choose to take a skin biopsy to make sure of their diagnosis. In this case, they’ll remove a layer of the lesion after numbing the area with a local anesthetic.
During childhood, a biopsy of a nevus sebaceous will be hairless and reveal immature sebaceous glands and hair follicles. In adults, the lesion will contain mature sebaceous glands and hair follicles, and a significant thickening of the epidermis.
Most nevi sebaceous will remain unchanged throughout an individual’s life, though some may develop tumors. These tumors are frequently benign, but if you notice any changes in the lesion, you should make an appointment with your dermatologist to make sure that they’re benign.
To look for complications — including skin cancer — your doctor may take a biopsy of the new growth or affected area.
Nevi sebaceous don’t automatically require treatment as long as they’re stable and unchanged, though they should be monitored closely for complications like bumps or sores that need to be checked. This is essential, as certain types of skin cancer like basal cell carcinoma and squamous cell carcinoma may also occur in as many as 22 percent of patients with a sebaceous nevus.
Some individuals will choose to have their nevus sebaceous removed entirely, due to either cosmetic reasons or complications. While they can be removed in a surgical excision, scarring is unavoidable and will be permanent after removal.
For those who do choose to reduce the appearance of their nevus sebaceous for cosmetic purposes or to prevent malignant growths, laser treatment can be an effective option. While laser treatments will still leave a scar, the scar may be potentially less noticeable than with surgical excision.
One 2005 study also found that there were no cases of recurrence after YAG laser treatment, though it was a small case study. More research is needed to determine a true efficacy rate. Carbon dioxide laser treatment is also a common treatment method.
Nevi sebaceous are rare congenital malformations, and can be difficult to remove. Fortunately, they are benign, and many stay that way throughout a person’s life. Even those that develop tumors typically have benign growths instead of malignant ones.
That being said, malignancies are a possibility so it’s important to get regular skin cancer checks with your dermatologist. You should also make an appointment with your dermatologist if you notice any changes to the lesion between appointments.
In some cases, you and your doctor may decide to remove the nevus sebaceous long before it gets a chance to produce malignant growths. In this case, excision or laser treatment are two good options.