What is Seborrheic Keratosis?
A seborrheic keratosis (seb-or-ree-ik kare-uh-toe-sis), also known as SK or seb ker, is a benign (non-cancerous) growth of surface skin cells with pigment (color).
“They can appear in a person’s twenties but are more common as people age. The growths are often scaly and beige or brown, even turning black over time,” says Franziska Ringpfeil, M.D., Assistant Professor of Dermatology at the Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia and owner of Ringpfeil Advanced Dermatology in Haverford, PA. “Many people are embarrassed by their ugliness and think they look like warts or moles. They are sometimes called senile warts, senile keratoses, or considered the ‘barnacles of old age’.” Does that warty growth bothering you sound like SK? Check out the list below of signs and symptoms, assembled by Dr. Ringpfeil and Joel Gordon, M.D., Fellow of the American Academy of Dermatology and a dermatologist in Greenfield, MA. Then go see a dermatologist for a proper diagnosis. SK and cancerous skin lesions, such as melanoma and basal cell carcinoma, can be easily confused. A dermatologist has special training to make the correct diagnosis, which could save your life. Any cancerous lesions should be treated before they increase in size or spread.
Signs and Symptoms
Appearance of SK
- They are usually round or oval, with clearly defined borders. The borders can be regular or irregular.
- They range in color and may appear white, flesh-colored, yellow, pink, grey, beige, dark brown, or black. The lesions in the brown spectrum are the most common. Sometimes, a lesion starts out beige and turns darker over time.
- They can be flat or raised. Often lesions start out flat and become thicker and scalier, or warty-looking, over time. Sometimes, SKs are smooth and waxy, appearing to be stuck onto the skin, as though you can scratch them off. Don’t pick at them though! Picking can make them bleed and cause an infection.
Location and Size of SK
- They can appear on your skin on any part of your body, except the palms, soles of the feet, or lips. They often appear on the scalp or face, especially around the temples, or on the neck, shoulders, back, chest or stomach. They are less commonly found on the buttocks or genitals.
- The lesions can be scattered around your body, or they may cluster. Areas of friction, like the crease beneath the breasts where a bra can rub, are common sites of clustered SKs.
- They range from a millimeter to a few centimeters wide. A lesion may also grow larger and thicker over time.
Symptoms of SK
- They are usually painless, though they can become irritated, inflamed, and painful.
- The lesions can be itchy on their own, but often they become itchy, or may even bleed, if they frequently rub against jewelry, clothing, or a seat belt. If they appear on a man’s face, they can interfere with shaving.
Age of Onset of SK and Number of Lesions
- They can begin to appear in a person’s 30s, or even 20s, but the number of lesions increases with age so people tend to notice SK lesions in their 40s and 50s.
- Dermatologists reported in a 2014 survey that among the SK patients who come to see them, the average number of lesions each patient has is 17*.
- Some people can develop a hundred or more of them, if they are genetically predisposed to them.
*Data on File: Aclaris Therapeutics Inc. Survey of 594 dermatologists.
How common is it?
Most people develop a seborrheic keratosis at some point in life. According to the American Academy of Dermatology and the Society for Investigative Dermatology, the growths affect over 83 million people in the United States. In one Australian study published in the British Journal of Dermatology, 100% of people ages 51 and older had the condition. This study and other studies suggest that, in addition to increasing age, ultraviolet radiation (from sun exposure) plays a role in determining who will develop SK. Seborrheic keratosis equally affects men and women. People with a genetic predisposition to SK are more likely to develop the lesions when they are younger, and to have many of them over their lifetime. The condition is more common among Caucasians than other ethnicities. However, people of color are also prone to developing seborrheic keratosis lesions. In particular, African Americans are more prone to develop a variant of seborrheic keratosis referred to as dermatosis papulosa nigra (or DPN), in which many smaller SK lesions are clustered on the face and around the eyes.