When Do You Need a Skin Biopsy to Diagnose Psoriasis?

Psoriasis symptoms can vary widely from flat, shiny scales to crusty red bumps anywhere on the body. Often, a doctor can simply examine the skin to confirm the symptoms of psoriasis and make a psoriasis diagnosis. She'll consider what the lesions look like, as well as where they're located on the body.

For instance, fingernails can show telltale signs of psoriasis because the disease can cause them to become thick and scarred with tiny pits. But sometimes diagnosing psoriasis requires more detailed study than a doctor can provide with the naked eye, making a skin biopsy necessary.

A skin biopsy is a simple procedure in which skin cells are taken from an affected area of the skin, such as a lesion, and examined under a microscope to confirm that the abnormalities in the skin cells really are psoriasis.

Psoriasis Skin Biopsy Step-by-Step

Skin biopsies for psoriasis are typically done in a doctor's office rather than a hospital, and they're usually performed by a dermatologist, who can choose from several different skin biopsy methods.

These are the steps in a skin biopsy for diagnosing psoriasis:

  1. Anesthesia is administered. The doctor will numb the area to be biopsied by injecting an anesthetic into the skin with a needle.
  2. Skin cells are removed. Typically, an excisional, punch, or shave biopsy is performed. An excisional biopsy involves cutting out a section of abnormal skin with a knife. A punch biopsy allows for removal of deeper skin cells by using a tool with a hollow area that "punches" out a small section of skin. A shave biopsy only involves scraping off the very top layer of skin cells from the affected area.
  3. Any bleeding is stopped. If there is bleeding during the process, the doctor uses a tool called a cauterizer that stops the blood flow.
  4. Depending on the type of biopsy, skin is stitched. If an excisional or punch biopsy is performed, the skin will be stitched up carefully to close the wound. A shave biopsy doesn't require stitches since the skin is not cut.
  5. The wound is covered. If the doctor removed a large lesion to examine, she may take a piece of skin from somewhere else on the body and attach, or graft, it to cover the area exposed by the biopsy.
  6. The sample is examined by a pathologist. The sample from your skin biopsy is sent to a lab, where a pathologist (a doctor trained to make a diagnosis by looking at cells under a microscope) examines your cells for indications of psoriasis.
  7. Your doctor gives you a diagnosis. Your doctor will probably have the results of your skin biopsy in about a week. She will tell you whether your symptoms indicate psoriasis or another skin condition.

It's important to get an accurate psoriasis diagnosis in order to treat the condition appropriately. Once your doctor knows what you have, you’ll be able to follow a treatment plan to help minimize skin lesions and reduce inflammation, itching, and pain.

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