LAUSR

An 81-year-old Chinese male presented with a 3-month history of a pruritic eruption on his trunk and upper limbs in May 2013. His past medical history included chronic obstructive pulmonary disease, benign prostatic hypertrophy, and hypercholesterolemia. No new medications were started preceding his skin eruption. On examination, there were excoriated erythematous papules and plaques over the abdomen, lower back, buttocks, and elbows. Skin biopsy revealed superficial perivascular inflammation with neutrophilic microabscesses in dermal papilla and no subepidermal blistering or eosinophilia (Fig. 1a). Direct immunofluorescence (DIF) from perilesional skin revealed granular deposits of IgA at the dermoepidermal junction with accentuation over the dermal papilla (Fig. 1b) consistent with dermatitis herpetiformis (DH). Indirect immunofluorescence (IIF) was negative. He did not have other signs suggestive of celiac disease, and serum anti-tissue transglutaminase antibodies were negative. He was treated with dapsone 50 mg/day and a gluten-free diet with good clinical response. In 2015, he was placed in a nursing home and developed a gradual worsening of his DH. There were concerns whether he concurrently developed bullous pemphigoid, and prednisolone 10 mg daily was added to dapsone 50 mg daily. A repeat skin biopsy for histology and DIF testing was consistent with DH, and BP 180 ELISA was negative. The dose of dapsone was increased to 75 mg daily, and prednisolone was tapered gradually over 6 weeks with some improvement. He subsequently developed a low-grade dermatitis on the arms and shins while on dapsone 75 mg daily