Dermatitis Herpetiformis Workup

Updated: Jun 06, 2018
  • Author: Jami L Miller, MD; Chief Editor: Dirk M Elston, MD  more...
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Workup

Laboratory Studies

The diagnosis of dermatitis herpetiformis (DH) is made on the basis of skin biopsy results. However, other tests should be performed depending on the presence of symptoms of associated syndromes. Serum markers, such as IgA endomysial antibodies, are negative in as many as 10-37% of patients with dermatitis herpetiformis. [32, 33] Arguments have been made in favor of testing for tissue transglutaminase for diagnosis, [34] but tissue transglutaminase enzyme-linked immunosorbent assay positivity can occur in many autoimmune diseases because of impurities and cross-reactivity. [35]

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Procedures

The diagnosis is made after observing characteristic findings from skin biopsy specimens. The biopsy sample should be taken from the edge of a lesion for hematoxylin and eosin staining and from normal-appearing perilesional skin for direct immunofluorescence staining.

Results of direct immunofluorescence of lesional skin are often falsely negative. The vigorous immune response degrades the IgA antibody at the site. Therefore, biopsy specimens for the direct immunofluorescence studies should be taken from healthy-appearing skin.

See the image below.

Immunofluorescence showing immunoglobulin A at the Immunofluorescence showing immunoglobulin A at the dermoepidermal junction (direct immunofluorescence stain).
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Histologic Findings

Biopsy specimens of lesional skin reveal neutrophils in the dermal papillae, with fibrin deposition, neutrophil fragments, and edema. Eosinophils may be present. Papillary microabscesses form and progress to subepidermal vacuolization and vesicle formation. Vesicles form in the lamina lucida, the weakest portion of the dermoepidermal junction, due to neutrophil lysosomal enzymes. [36] See the image below.

Papillary microabscesses form and progress to sube Papillary microabscesses form and progress to subepidermal vacuolization and vesicle formation in the lamina lucida, the weakest portion of the dermoepidermal junction (hematoxylin and eosin stain).

The histologic differential diagnosis of early skin lesions includes bullous lupus erythematosus, bullous pemphigoid, epidermolysis bullosa acquisita, and linear IgA disease. [37] The histologic differential diagnosis of late skin lesions includes bullous drug eruption, bullous pemphigoid, erythema multiforme, and herpes gestationis.

Granular IgA deposits in dermal papillae of perilesional skin observed by direct immunofluorescence is the criterion standard of diagnosis. However, the presence of both granular and linear IgA deposits has been reported on direct immunofluorescence testing in a patient with dermatitis herpetiformis. [38, 39]

Inflammation in lesional skin degrades the immunoreactants and is usually negative for the diagnostic granular pattern. Because deposits are found more reliably in the surrounding normal-appearing skin, the standard practice is to obtain biopsy specimens from normal-appearing perilesional skin for direct immunofluorescent staining.

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