Neutrophilic urticarial dermatosis and Sweet-like neutrophilic dermatosis: under-recognized neutrophilic dermatoses in lupus erythematosus.

Background/Objectives Neutrophilic dermatoses can be associated with autoimmune connective tissue diseases such as systemic lupus erythematosus (SLE). We analyzed clinical and histological features of neutrophilic urticarial dermatosis (NUD) and Sweet-like neutrophilic dermatosis (SLND)-the most recently delineated entities of the neutrophilic dermatoses. Methods We retrieved database medical records of patients with SLE whose skin biopsy demonstrated a neutrophilic-predominant infiltrate of the skin, and included those whose biopsies revealed findings of SLND or NUD. Results SLND skin lesions lasted longer than those of NUD and were localized to sun-exposed areas. All NUD cases resolved within one week either spontaneously or with treatment such as antihistamines, but SLND skin lesions lasted longer than one week; prednisone was used in four of these five patients. All NUD cases were found in existing SLE patients and were not associated with systemic signs of flare-up of SLE. However, 80% of SLND cases experienced flare-up of SLE; and in 60%, SLND developed concomitantly with SLE as a presenting sign. Conclusion Different clinical courses and relationships with SLE suggest that NUD and SLND have different pathogeneses for neutrophilic inflammatory reactions.