Dermatitis Herpetiformis

 Photoclinic

For 10 years, a 45-year-old man had a recurrent nonpruritic rash on his upper outer arms (A) and lateral trunk (B). The shallow crusted ulcerations, some with scarring, arose as a small papule. The top of the lesion then ulcerated and healed, leaving brown hyperpigmentation. In the past 6 months, similar lesions occurred on his scalp. His mother had a nearly identical rash for about 8 years.

Multiple biopsies of the lesions were performed. The specimens were reviewed by a pathologist as well as a dermatologist who, after examining the patient, diagnosed dermatitis herpetiformis. Histopathologic findings pointed to a nonspecific neutrophilic vasculitis. Results of immunofluorescent studies showed no linear deposits of IgA or other immunoglobulins or complement in the basement membrane zone but revealed weak to moderate granular deposits of IgA in normal skin; these findings are suggestive of dermatitis herpetiformis. No perivascular deposits or immunoreactants were detected. Epidermal nuclear fluorescence and intercellular staining within the epidermis showed no immunoglobulins or complement. Results of serum studies with indirect immunofluorescence for epidermal antibodies and IgG and a test for endomysial IgA antibody (tissue transglutaminase) were negative. The glucose-6-phosphate dehydrogenase level and complete blood cell (CBC) count were normal.

The differential diagnosis includes linear IgA dermatitis, which is usually associated with little if any pruritus, and drug-associated IgA dermatitis. Dermatitis herpetiformis is usually associated with pruritus, which this patient denied, and a subclinical gluten-sensitive enteropathy.¹

The patient was treated with dapsone, 100 mg/d, and his CBC count was monitored weekly for 1 month. This regimen was repeated 2 years later. After both courses of therapy, the lesions partially resolved following the first 2 weeks of treatment, and the rash has recurred less frequently. ■

REFERENCE:

1.Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. Philadelphia: Mosby; 2004:554.