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How is dermatitis herpetiformis diagnosed?

A skin biopsy is used to confirm a diagnosis of dermatitis herpetiformis (DH). Dermatologists usually use what’s called a punch biopsy to remove some skin and test it for dermatitis herpetiformis. After injecting a local anesthetic, your dermatologist will use a tiny, cookie-cutter-like punch to remove a 4 millimeter (mm) sample of skin. The incision can be closed with one stitch and generally heals with very little scarring.

The skin sample is taken from the area next to a bump or blister, and a fluorescent dye is used to look for the presence of immunoglobulin A (IgA) deposits that appear in a granular pattern. Skin biopsies of people with DH are almost always positive for this granular IgA pattern.

It is important to have your dermatitis herpetiformis skin biopsy performed by someone who has diagnosed the skin condition before and knows how to do the biopsy. The skin sample must be taken from skin directly adjacent to the suspected dermatitis herpetiformis blister, as opposed to directly from the blister, since inflammation in the blister can destroy the IgA deposits.

Blood tests for other antibodies commonly found in people with celiac disease -- anti-endomysial and anti-tissue transglutaminase antibodies -- can help support the diagnosis of DH. If the antibody tests are positive and the skin biopsy has the typical findings of DH, people do not need an intestinal biopsy to confirm the diagnosis of celiac disease.

In addition to looking at the appearance of the rash, your doctor may order a skin biopsy to diagnose dermatitis herpetiformis. The skin biopsy allows the doctor to take a sample of your skin to check for certain antibodies that indicate dermatitis herpetiformis. A blood test may also be taken to look for these antibodies.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.