Dermatitis Herpetiformis - Diagnosis

Diagnosis

See also: List of human leukocyte antigen alleles associated with cutaneous conditions

Dermatitis herpetiformis is often misdiagnosed, being confused with drug eruptions, contact dermatitis, dishydrotic eczema (dyshidrosis), and even scabies.

Diagnosis is confirmed by a simple blood test for IgA antibodies, and by a skin biopsy in which the pattern of IgA deposits in the dermal papillae, revealed by direct immunofluorescence, distinguishes it from linear IgA bullous dermatosis and other forms of dermatitis. These tests should be done before the patient starts on a gluten-free diet, otherwise they might produce false negatives. If the patient has already started a gluten-free diet (there is a strong relationship with DH and coeliac sprue), it might be necessary for them to restart gluten for some weeks before the tests can be done reliably.