Fever and Painful Skin Lesions: When to Consider Sweet's Syndrome

Sweet's syndrome is an acute febrile neutrophilic dermatosis characterised by fever, neutrophilia, and painful cutaneous lesions. We describe a case of a 31-year-old male admitted with a two-week history of fever up to 39°C and painful erythematous papules, scattered and coalescing into plaques over the trunk and limbs, together with pustules on an erythematous base over the palms and dorsum of the hands. No relevant epidemiological exposure or recent drug exposure was identified. Investigation showed an erythrocyte sedimentation rate of 40 mm/h, leucocytosis of 14,380/µL with 77% neutrophils and no eosinophilia, and a C-reactive protein of 1.21 mg/dL. Liver and renal function, albumin, lactate dehydrogenase, serum iron, ferritin, and serum protein electrophoresis were normal, and a respiratory viral panel was negative. Blood, urine, and pustule cultures, an interferon-gamma release assay, and serology for human immunodeficiency virus, syphilis, hepatitis A, B, C, and E viruses, cytomegalovirus, and Epstein-Barr virus were negative, as was an autoantibody panel. Serum immunoglobulin A was below the detection limit (<0.07 g/L) before corticosteroid therapy and on all repeat measurements, including after treatment had been discontinued, with normal immunoglobulin G and M, and IgG-based coeliac serology was negative. Computed tomography of the chest, abdomen, and pelvis and peripheral blood immunophenotyping showed no abnormalities. A skin biopsy demonstrated intraepidermal blisters and a superficial perivascular neutrophilic infiltrate without vasculitis, spongiform pustules, or psoriasiform changes. The clinical and laboratory criteria for classical Sweet's syndrome were fulfilled, and the histology was compatible with, although not classical for, the syndrome. Prednisolone 60 mg/day (approximately 0.6 mg/kg/day) was started on clinical suspicion of the syndrome. After one week, the fever had resolved, but the lesions worsened slightly, prompting escalation to 100 mg/day (approximately 1 mg/kg/day), after which they regressed progressively and resolved completely within three weeks of dose escalation, with normalisation of the leucocyte count. Corticosteroids were tapered and discontinued before the three-month assessment, at which there was no relapse and no evidence of malignancy. This case illustrates three practical points: an acral pustular morphology does not exclude the diagnosis; early worsening under corticosteroid therapy may reflect an initial dose insufficient for body weight rather than an incorrect diagnosis, once infection has been rigorously excluded; and the coexisting finding of selective immunoglobulin A deficiency carries independent implications for coeliac disease screening and long-term follow-up.