Neutrophilic Urticarial Dermatosis in Systemic Lupus Erythematosus: A Diagnostic Challenge.

Neutrophilic urticarial dermatosis (NUD) is a rare condition that clinically resembles urticaria but is distinguished histopathologically. Given the overlap of clinical and histopathologic features between NUD, urticaria, and urticarial vasculitis (UV), distinguishing between these diagnoses is crucial, as their treatments differ significantly. A 47-year-old woman with systemic lupus erythematosus (SLE) presented with a mildly pruritic, burning rash for one week. Physical examination revealed erythematous, edematous wheals on her trunk and proximal extremities, indistinguishable from urticaria. A skin biopsy revealed a moderately dense infiltrate of neutrophils and nuclear dust with intact vessels, consistent with neutrophilic urticarial dermatosis (NUD). The lesions resolved with a prednisone taper. NUD should be considered in patients with SLE who present with urticaria-like eruptions unresponsive to antihistamines. Early biopsy and recognition of NUD can prevent misdiagnosis and inappropriate escalation of immunosuppressive therapy.