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Getting Diagnosed#

Medical Disclaimer

This guide is for informational purposes only. It is not medical advice. Read the full disclaimer.

DH is one of the most misdiagnosed skin conditions. The average time from symptoms to correct diagnosis is over 3 years, and many patients see multiple doctors before anyone identifies it. Understanding what tests you need can help you advocate for yourself.

Why DH gets misdiagnosed#

DH is frequently misdiagnosed as:

  • Eczema / atopic dermatitis (most common)
  • Contact dermatitis
  • Scabies
  • Psoriasis (especially scalp lesions)
  • "Nonspecific dermatitis" — a catch-all that delays real investigation

Several factors contribute:

  • DH is rare — many dermatologists see only a handful of cases in their career
  • Intact blisters are rarely seen — patients scratch them before their appointment
  • Many DH patients have no digestive symptoms, so celiac is never considered
  • It requires a specific biopsy technique that many doctors don't know about

Patient stories: Patient Experiences documents the diagnostic journey in detail

The gold standard: direct immunofluorescence (DIF) biopsy#

This is the single most important test for DH. If you suspect DH, this is the test to ask for.

What it is#

A skin biopsy examined under fluorescent microscopy for IgA antibody deposits.

Critical detail: where to biopsy#

The biopsy must be taken from uninvolved skin next to a lesion (perilesional skin) — NOT from the rash itself. Inflammation in active lesions destroys the IgA deposit pattern that makes the diagnosis.

This is the most common reason DH biopsies fail. If your doctor biopsies the lesion itself, the test may come back negative even if you have DH.

What a positive result looks like#

Granular IgA deposits at the tips of the dermal papillae. This pattern is pathognomonic for DH — meaning it essentially confirms the diagnosis with ~95-100% specificity.

What to tell your doctor#

"I'd like a skin biopsy for direct immunofluorescence, taken from uninvolved skin adjacent to an active lesion, to look for granular IgA deposits. This is the gold standard for diagnosing dermatitis herpetiformis."

Supporting tests#

Histopathology (H&E biopsy)#

A standard biopsy of an active lesion (separate from the DIF biopsy). This looks for neutrophilic microabscesses at the dermal papillae — supportive but not specific to DH on its own.

Blood tests (serology)#

Test What it measures Notes
Anti-TG2 IgA Gut autoimmunity (celiac marker) Positive in 70-95% of untreated DH patients
Anti-TG3 IgA Skin-specific autoimmunity Emerging as the primary DH-specific blood marker
EMA IgA Endomysial antibodies Very specific (~99%) but less sensitive in DH
Total serum IgA Rules out IgA deficiency Important — IgA deficiency causes false negatives on all IgA-based tests
Anti-DGP IgA/IgG Deamidated gliadin peptides Useful backup, especially if IgA deficient

A negative blood test does not rule out DH. Blood tests can be negative in mild or early disease. The DIF biopsy is the definitive test.

Small bowel biopsy#

Your gastroenterologist may recommend an endoscopy to check for intestinal damage. Over 90% of DH patients have celiac enteropathy, though it's often mild and symptom-free.

Full diagnostic science: Epidemiology & Diagnosis

The diagnostic checklist#

  1. Clinical suspicion — Symmetric, itchy papulovesicles on elbows, knees, buttocks, scalp
  2. Two skin biopsies — One from an active lesion (H&E), one from adjacent uninvolved skin (DIF)
  3. Blood work — Anti-TG2 IgA, total serum IgA, consider anti-TG3 IgA
  4. Consider endoscopy — Check for intestinal involvement
  5. Response to dapsone — Rapid improvement (1-3 days) provides therapeutic confirmation

If your doctor is resistant#

Some patients encounter physicians who dismiss DH or refuse to order the right tests. If this happens:

  • Ask specifically for DIF — name the test. Some doctors don't think to order it.
  • See a dermatologist — primary care physicians are less likely to consider DH
  • Request a celiac panel — even without GI symptoms, this can raise clinical suspicion
  • Get a second opinion — patients frequently need to see multiple doctors before getting diagnosed
  • Don't accept "nonspecific dermatitis" without a DIF biopsy — this catch-all diagnosis delays proper investigation

Important: don't go gluten-free before testing#

If you eliminate gluten before getting tested, your antibody levels will drop and the DIF biopsy may become negative. Get tested first, then start the diet.

If you've already started a gluten-free diet, discuss a gluten challenge with your doctor — reintroducing gluten for a period before testing to ensure accurate results.

Next steps#

Once diagnosed, learn about your treatment options:

Treatment Basics