Comparison of Clinical Characteristics Between Bullous and Non-bullous Rheumatoid Neutrophilic Dermatosis: A Case Report, Literature Review, and Proposed Diagnostic Criteria.

Rheumatoid neutrophilic dermatosis (RND) is associated with rheumatoid arthritis and typically presents as papules, nodules, and/or plaques bilaterally on the extremities. Rarely, vesiculobullous lesions (bullous RND) may occur. We herein present a case of bullous RND diagnosed in our department. A 70-year-old Japanese woman presented with multiple painful, tense bullae, accompanied by pustules, erythematous papules, and erosions on the lower extremities, and a few hemorrhagic bullae were observed on the soles. Her medical history included seropositive rheumatoid arthritis for 14 years, which was successfully treated with oral prednisolone and tacrolimus hydrate, but joint pain and swelling developed one month before her visit to our department. A skin biopsy of the blister on the lower leg revealed an intraepidermal and subepidermal blister, containing numerous neutrophils. Marked neutrophilic infiltration, showing prominent leukocytoclasis, was observed in the dermis without vasculitis. Direct immunofluorescence yielded negative results. Bacterial cultures from the blisters were sterile. Taken together, the diagnosis of bullous RND was made. Despite treatment with oral minocycline for one week, new skin lesions developed. Treatment was switched to dapsone at 75 mg daily, resulting in the improvement of skin lesions and arthralgia within one week. In this report, we describe a case of bullous RND and compare the differences in clinical findings between bullous and non-bullous RND, which have not been previously documented. Additionally, as RND and Sweet's syndrome share overlapping clinicopathological features, we proposed five diagnostic criteria for RND: (1) a definitive diagnosis of rheumatoid arthritis; (2) high rheumatoid arthritis disease activity; (3) multiple erythematous papules, nodules, plaques, and/or tense vesiculobullous lesions; (4) predominantly neutrophilic dermal infiltrate without leukocytoclastic vasculitis; and (5) microbial sterility.