From the Guidelines
No, a Direct Immunofluorescence (DIF) test is not expected to be negative for dermatitis herpetiformis in an intestinal biopsy, as the characteristic finding is the presence of granular IgA deposits, which is a diagnostic criterion for the disease. However, it's essential to note that DIF is typically performed on skin biopsies, not intestinal biopsies, to diagnose dermatitis herpetiformis. The presence of granular IgA deposits in the dermal papillae of uninvolved perilesional skin is the major diagnostic criterion for dermatitis herpetiformis, as stated in the guidelines from the British Society of Gastroenterology 1.
When considering intestinal biopsies, the findings may vary, with approximately 70% of patients with dermatitis herpetiformis showing abnormality of the small intestinal mucosa with either total or subtotal villous atrophy, and a further 25% having normal villous architecture with increased intraepithelial lymphocytes (IELs) 1.
In the context of dermatitis herpetiformis, the diagnosis should not be made unless the presence of granular IgA deposits in the dermal papillae has been confirmed by DIF on skin biopsy. If a negative result is obtained but clinical suspicion remains high, consider repeating the biopsy from a different site or temporarily discontinuing dapsone treatment, which can affect results. It's crucial to prioritize the diagnosis based on the most recent and highest quality evidence, which emphasizes the importance of DIF in diagnosing dermatitis herpetiformis 1.
Key points to consider:
- DIF is typically performed on skin biopsies, not intestinal biopsies, to diagnose dermatitis herpetiformis.
- The presence of granular IgA deposits in the dermal papillae is the major diagnostic criterion for dermatitis herpetiformis.
- Intestinal biopsies may show varying degrees of villous atrophy or increased IELs in patients with dermatitis herpetiformis.
- A negative DIF result does not rule out the diagnosis if clinical suspicion remains high, and further evaluation or repeat biopsy may be necessary.
From the Research
Direct Immunofluorescence (DIF) Test in Dermatitis Herpetiformis
- The DIF test is a crucial laboratory procedure in diagnosing dermatitis herpetiformis (DH) 2.
- The test detects granular immunoglobulin A (IgA) deposits in the dermal papillae or at the dermal-epidermal junction, which is a characteristic feature of DH 3, 4.
- However, the DIF test may not always be positive in patients with DH, especially in those with mild intestinal damage or normal mucosa 5.
- In some cases, the DIF test may show deposition of exclusively C3 at the dermal-epidermal junction, which is referred to as "granular C3 dermatosis" 2.
- It is essential to note that a negative DIF test result does not rule out the diagnosis of DH, and other diagnostic tests, such as serologic tests for celiac disease, may be necessary to confirm the diagnosis 5, 6.
Intestinal Biopsy in Dermatitis Herpetiformis
- Intestinal biopsy is not always necessary for the diagnosis of DH, especially in patients with proven DH and celiac disease 4.
- However, in some cases, intestinal biopsy may be performed to assess the degree of enteropathy and to rule out other conditions 5.
- The DIF test on intestinal biopsy samples may not always be positive in patients with DH, and the test results should be interpreted in conjunction with other diagnostic tests and clinical findings 5.