Doctors can often determine a psoriasis diagnosis by simply examining a person’s skin for telltale symptoms. Sometimes, though, a person’s symptoms may resemble those of other skin condiitons, and a skin biopsy may be necessary. This minor procedure, where a small sample of skin is taken and examined under a microscope, can confirm whether those troublesome patches are psoriasis or something else.

Psoriasis is a long-term skin condition in which your body produces skin cells too quickly, leading to inflammation. Normally, our skin takes about a month to shed old cells and replace them with fresh ones. But in people with psoriasis, this cycle speeds up dramatically and finishes in just a few days. This doesn’t leave enough time for old skin to flake off, leading to a pile-up on the surface.

It’s important to seek a diagnosis from a health care professional if you think you may have psoriasis. Psoriasis symptoms can be confused with other conditions, such as eczema. For this reason, psoriasis is most commonly diagnosed by a dermatologist — a doctor specializing in conditions of the skin, hair, and nails. They may rule out the possibility of other conditions and determine if psoriasis is causing your symptoms.

Psoriasis is generally diagnosed through a physical examination. If a physical exam isn’t enough to diagnose the condition, a dermatologist may order a skin biopsy.

What Is a Skin Biopsy?

A skin biopsy is a procedure that involves removing a small skin sample for testing. Doctors called pathologists examine this skin sample under a microscope to check for signs of skin diseases or conditions like psoriasis. Standard skin biopsies can be performed in a dermatologist’s office or another outpatient health care facility.

There are three main types of skin biopsies: shave biopsy, excisional biopsy, and punch biopsy.

Shave Biopsy

During a shave biopsy, a doctor uses a tool similar to a razor blade to remove a small section of the top layers of skin (the epidermis and a portion of the dermis). This procedure is commonly done to look for skin cancers in the top layers of the skin.

Excisional Biopsy

An excisional biopsy involves using a small knife known as a scalpel to remove an abnormal area of skin, as well as a portion of normal skin. Excisional biopsy goes down to or through the fatty layer of skin. This procedure is usually done when a dangerous type of cancer is highly suspected.

Punch Biopsy

A punch biopsy is most commonly used to diagnose psoriasis. A punch biopsy involves using a circular tool to remove a small section of deeper layers of skin (the epidermis, dermis, and superficial fat). A circular piece of skin with a 3-millimeter diameter is usually biopsied by the punch method.

What To Expect During a Punch Biopsy

The name “punch biopsy’ refers to the technique used to remove the skin sample. During a punch biopsy, the skin is numbed usually by injecting anesthetic into the skin. The doctor uses a device similar in size and shape to a pencil to puncture the skin. One or two stitches may be needed to close the wound after the skin sample has been taken out.

The biopsy typically takes about 15 minutes from start to finish, including the time it takes to prepare, dress the wound, and provide instructions for home care. After the biopsy, your skin sample will be sent to a laboratory for examination. The results of a skin biopsy should be ready in about one week.

What Else Is Involved in Diagnosing Psoriasis?

There are five main types of skin psoriasis. During diagnosis, your doctor may assess your signs and symptoms to diagnose you with one of the following:

• Plaque psoriasis (the most common type of psoriasis)
• Guttate psoriasis
• Inverse psoriasis
• Pustular psoriasis
• Erythrodermic psoriasis

Doctors identify which type of psoriasis a person has by their symptoms.

Psoriasis is generally diagnosed clinically. This means that most of the time, doctors can tell if you have psoriasis just by looking at your skin and talking to you about your symptoms. Clinical diagnosis involves providing a diagnosis based on your medical history, signs, symptoms, and a physical exam.

In most cases, a dermatologist can diagnose psoriasis with an examination alone. A skin biopsy may have to be done if a dermatologist needs more information to rule out other potential causes of your symptoms, such as skin conditions that may resemble psoriasis.

During a physical exam, a dermatologist will look at your skin, taking note of any discolored, flaky, dry patches of skin (plaques). They will likely examine the size, location, and shape of these plaques, as well as where they are located on your body. A dermatologist may also ask about any joint symptoms and examine your nails for signs of pitting, ridges, or separation from the nail bed, all of which point to psoriatic arthritis.

In short, figuring out if you have psoriasis isn’t always straight to the point. Sometimes, just looking at your skin gives the doctor enough clues, but other times, they need to dig a bit deeper. That’s where a skin biopsy comes in handy, especially when your condition is a bit unclear.

Knowing what psoriasis is and how doctors check for it, including using different types of skin checks like a skin biopsy, helps you get the right treatment.

Find Your Team

MyPsoriasisTeam is the social network for people with psoriasis and psoriatic arthritis and their loved ones. On MyPsoriasisTeam, more than 126,000 members come together to ask and answer questions, offer support, and share their stories of everyday life with psoriasis and psoriatic arthritis. Members frequently talk about what it was like to be diagnosed with psoriasis.

Did you need a skin biopsy to be diagnosed with psoriasis? Share your experience with others in the comments below, or make a new post on your Activities page.