A pruritic rash characterized by pink, scaly plaques with a few crusted erosions on the elbows (Figure), knees, lower back, and buttocks developed in a 42-year-old man. He was otherwise healthy and took no medications. Review of systems was negative, although there was a strong positive family history of celiac disease.
Differential diagnosis included dermatitis herpetiformis, bullous pemphigoid, granuloma annulare, and palisaded neutrophilic and granulomatous dermatitis.
Key points: Punch biopsy from the edge of a blister revealed a subepidermal vesicle with neutrophilic infiltration along the dermo-epidermal junction, and a superficial mixed inflammatory infiltrate of neutrophils, lymphocytes, and eosinophils. Direct immunofluorescence revealed granular deposition of IgA and C3 along the basement membrane. Laboratory examination revealed elevated levels of transglutaminase and anti-gliadin antibodies.
Based on the clinical, histologic, and laboratory findings, dermatitis herpetiformis was diagnosed. Treatment with triamcinolone 0.1% cream twice daily and a gluten-free diet were needed to clear the condition.
Notes: Patients with dermatitis herpetiformis deserve consultation with a gastroenterologist for evaluation and follow-up. Once a diagnosis of celiac disease is confirmed by colonoscopy, a gluten-free diet should be instituted. Although the eruption may respond to dapsone or sulfasalazine, failure to comply with a strict gluten-free diet confers an elevated risk of GI lymphoma, which occurs in approximately 5% of patients.