(BMJ)—A woman in her 80s presented with an 11-day hx of red papules on her forearms. PMHx: Sixteen-year hx of RA. Exam: Afebrile. Tender red papules and nodules on bilateral forearms. Labs: High WBC and inflammatory markers. What’s the dx?
Rheumatoid neutrophilic dermatitis
Sweet syndrome
Erythema nodosum
Hypersensitivity drug reaction
Contact dermatitis
You are correct. Bx of the lesions showed perivascular and diffuse neutrophilic infiltrates without any identifiable infectious agents or fibrinoid necrosis, differentiating the condition from true vasculitis. Despite a lack of fever on presentation, the bx results confirmed the dx of Sweet syndrome.

Sweet syndrome is characterized by the abrupt appearance of erythematous papules, plaques, or nodules on the skin, along with leukocytosis and, in most cases, fever. Extracutaneous involvement such as hepatitis and encephalitis can occur. RA is rarely associated with Sweet syndrome; it occurs in only 1% of RA cases.

Consider Sweet syndrome in patients with RA who present with abrupt onset of characteristic skin lesions, raised inflammatory markers, and fever.

BMJ 2022;376:e07667