Origins of annoying seborrheic keratoses are a mystery

ASK THE DOCTORS By Robert Ashley, M.D.

Dear Doctor: I’m 88 and have small, brown, rough — and very itchy — spots that develop on my back and other areas. If I can scratch them off, the itching goes away. One spot that I didn’t scratch off is now embedded and I can’t get it off. Two dermatologists have basically said, “It’s your age. Live with it.” Isn’t there another answer?

Dear Reader: You seem to be describing seborrheic keratoses (the singular is keratosis). These scaly, thickened growths appear to be “stuck” on the skin, sort of like wall putty. Like wall putty, these lesions can often be scraped off; unlike putty, however, they can come back on their own. Although most lesions are brown, they can also be white, black, yellow or grayish. They normally appear after the age of 50 (so, yes, they are common at your age), but can begin in one’s 30s.

Seborrheic keratoses can occur anywhere upon the body except the palms and soles, and the lesions are more likely to occur in sun-exposed areas of the body. Some people have a few lesions; others may have hundreds. Such keratoses can be irritated by clothing — especially bras — leading to itching, pain and bleeding.

Although the sun may be a factor in the development of such lesions, their origin largely remains a mystery. We do know that when normal cell death is disrupted, skin cells accumulate, bunching up on top of each other. It’s possible this disruption is caused by a genetic mutation in the skin cells; in fact, the likelihood of such lesions does seem to be influenced by genetics.

Because the lesions resemble warts, many medical experts have postulated that the human papilloma virus (HPV), which creates warts, is the cause. A 2004 study took biopsies of seborrheic keratoses from 55 people and compared them with 48 biopsies of normal skin in other individuals. Although the researchers found HPV in 76 percent of the keratoses, they couldn’t conclude that HPV was the cause.

Doctors are usually not worried about seborrheic keratoses (as your experience attests), because the likelihood of them becoming cancerous is extremely small. But although the lesions are not harmful, they’re not pretty either, which is the primary complaint against them. The basic treatment is to try to destroy them, especially if they’re causing irritation. Biopsies are rarely necessary unless something about the lesion looks cancerous.

Liquid nitrogen is often the first choice of doctors trying to destroy seborrheic keratoses. It makes the lesions blister and then fall off — which may be a good option if it is overly itchy or painful — but the lesions can return. Doctors can also shave off the lesions, but this can lead to bleeding and scarring. Laser therapy can remove the lesions as well, but is rarely used.

As for topical treatments, the retinoid cream tazarotene can diminish seborrheic keratoses, as can a topical medication used for warts, imiquimod.

In the future, when science has figured out the cause for seborrheic keratoses, doctors will be more apt to prevent these lesions from occurring, perhaps through a vaccine. In the meantime, if these lesions are not physically irritating, there is no pressing need for treatment. So, you may just have to live with it.

Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.