This is what looks like—on your nails.

Most people familiar with the chronic skin condition know that psoriasis causes trademark red, itchy, scaly buildups called plaques. But a new case report in the New England Journal of Medicine (NEJM) highlights one of the less common symptoms of psoriasis: nail pitting.

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In the report, Juan A. Moreno-Romero, MD and Ramon Grimalt, MD of Barcelona detail the case of a 28-year-old, unnamed male patient who showed up at a dermatology clinic to discuss changes to his fingernails that had been developing over three years. He had small depressions, also called pits, and yellow discoloration across the nails of both hands.

 cleanString alt NEJM.org

Turns out, he also had scaly plaques on his elbows and knees, and his doctors diagnosed him with psoriasis, which is thought to affect up to 3% of people worldwide, according to the National Psoriasis Foundation. The autoimmune disease usually first appears between ages 15 and 25, according to the NPF, although anyone can get it at any age.

While nail changes might not be the first thing that comes to mind when you think of a skin condition, they’re actually common in people with psoriasis, the doctors wrote. In addition to pitting and discoloration, psoriasis can also make or lift from the nail beds (called onycholysis). While nail changes are most common in people with —a type of arthritis that develops in people with psoriasis—the patient in the NEJM case report “had no joint tenderness, swelling, or stiffness,” his doctors wrote.

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Nail pitting often tips off doctors that psoriasis could be to blame, although it’s not the only health concern that can cause these tiny dents. “Other conditions in which nail pitting can be seen include alopecia areata, eczematous dermatitis, and traumatic occupational injury,” according to the report.

If you notice pitting on your own nails, don't ignore it; talking to a doctor can help you get the right treatment. It worked for the NEJM patient. After six months of treatment—which involved applying a type of steroid in the form of a nail lacquer—his nail pitting and his skin plaques had cleared.

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