Make the Diagnosis

Make the Diagnosis - May 2017

A 47-year-old Hispanic male presented with a 2-year history of severely pruritic papules on the elbows, knees, buttocks, and scalp. He reported no relief with antihistamines or topical antifungal treatments. His review of systems was negative for any associated symptoms including gastrointestinal complaints. On physical examination, urticarial papules and vesicles with excoriations were noted on the elbows and knees.

What is your diagnosis?

Herpes folliculitis

Dermatitis herpetiformis

Papular urticaria

Dermatitis herpetiformis

Dermatitis herpetiformis (DH) is an uncommon disorder that occurs most often in those of Northern European descent and is seen more frequently in men than women. DH is a disease of predominantly autoimmune origin, representing an aberrant host response to epidermal transglutaminase. DH is strongly linked to celiac disease, a gluten-sensitive enteropathy. The proposed pathophysiology of DH involves an initial autoimmune response to gliadin, a gluten-derived peptide that is delaminated by tissue transglutaminase. Individuals with HLA-DQ2 and HLA-DQ8 have significantly increased risk of development of DH because of the haplotype’s increased affinity for tissue transglutaminase-modified gliadin. With epitope spreading, IgA antibodies against epidermal transglutaminase are formed, and the clinical manifestations of DH become apparent. The association between DH and gluten exposure is strongly supported by the observed resolution of symptoms upon the patient’s adherence to a strict gluten-free diet.

The primary lesions of DH are vesicles and papules in a grouped or “herpetic” formation. However, as these lesions are extremely pruritic, the primary lesions may be absent in many cases and instead replaced by secondary excoriations and erosions. DH has a very classic distribution pattern, particularly involving the bilateral extensor surfaces, buttocks, and scalp. Although some cases of oral DH have been reported, mucosal involvement is generally considered to be very rare.

Despite its strong association with underlying celiac disease, most patients with DH do not report any associated gastrointestinal symptoms. Those with DH may present with any variety of other autoimmune conditions, with hypothyroidism being the most common. Interestingly, patients with DH have been shown to be at an increased development of non-Hodgkin lymphoma. It is not certain whether adherence to a strict gluten-free diet reduces this risk in this population.

Diagnosis can be made with a proper clinical history and examination, tissue pathology, direct immunofluorescence microscopy (DIF), and/or serology, with DIF being the most definitive. Perilesional skin is preferred for DIF, as lesional biopsies have been found to have higher rates of false negative results. The characteristic DIF finding diagnostic of DH is granular IgA deposits within dermal papillae, which was seen in this patient’s DIF.

Adequate treatment of DH can usually be accomplished with a combination of dapsone and a gluten-free diet. Initially, dapsone may be used for more immediate relief of associated pruritus and other bothersome symptoms. A strict gluten-free diet should be implemented as soon as possible, and dapsone can be tapered approximately 2-3 months after initiation as to avoid potential adverse effects with longterm treatment at higher doses.

The case and photo were submitted by Natasha Cowan, BS, University of California, San Diego, School of Medicine, and Nick Celano, MD, of San Diego Family Dermatology.

Dr. Bilu Martin is a board-certified dermatologist in private practice at Premier Dermatology, MD, in Aventura, Fla. More diagnostic cases are available at edermatologynews.com. To submit a case for possible publication, send an email to [email protected].

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