skin biopsy being performed in a dermatologist's office

What Can I Expect from a Skin Biopsy for Psoriasis? A Q&A with Dr. Truong

By Beth W. Orenstein
August 11, 2023

This article is part of a Q&A series in which a healthcare professional in our community answers your frequently asked questions.

We asked: “I have psoriasis. Why did my doctor order a skin biopsy? What can I expect?”

Allison Truong, M.D.: Your dermatologist most likely can diagnose psoriasis just by looking at your skin for symptoms. If it’s plaque psoriasis, they’ll see the telltale silvery, scaly plaques. For other types of psoriasis—such as inverse or pustular psoriasis—what it looks like and where on your body it appears may be enough for a diagnosis.

However, if your symptoms are a bit different or you’re not responding to standard psoriasis treatments, your doctor might order a psoriasis biopsy to confirm the diagnosis or look to see whether you have another skin condition.

A biopsy for psoriasis can be done in your doctor’s office and should take about 10 to 15 minutes.

A punch biopsy is the most common type for diagnosing the disease. To perform a punch biopsy for psoriasis, the doctor will clean the area and then numb it with an injection of lidocaine and epinephrine. (Note: The doctor will use lidocaine or normal saline if you’re pregnant or have a sensitivity to epinephrine.) The doctor then uses a pencil-shaped tool to remove a small, circular sample of your skin that is a few layers deep.

Usually, a stitch or two is required to close the wound. You typically go home with a little petroleum jelly and a bandage over the area.

Doctors can perform a psoriasis biopsy anywhere on the body—including the scalp, torso, buttocks, and feet. The size of the sample needed depends on the area being tested. Oftentimes, a 4-millimeter punch tool is used, so the sample taken is a little less than half a centimeter.

The skin sample is then sent to the lab where a specialist in skin pathology called a dermatopathologist looks at it under a microscope. In a few days, your doctor will report the findings to you. Depending on the area of biopsy, the sutures will be removed within seven to 14 days.

The risks of biopsy are bleeding, infection, and scarring. If you do get a scar, it’s usually small and rarely visible.

The benefit of a psoriasis biopsy: a definitive diagnosis.

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