Sweet Syndrome-Associated ANCA-Negative Vasculitis

Introduction: Sweet syndrome (SS) is characterized histologically as a neutrophilic dermatosis. It typically presents with fever and an asymmetric, painful, erythematous rash. Lab abnormalities include leukocytosis with predominant neutrophilia, elevated ESR and CRP. It can be drug-induced, infection-related, malignancy associated, or part of a systemic inflammatory disease. SS has been associated with ANCA-associated vasculitis (AAV). The syndrome can predate, occur simultaneously, or follow the onset of AAV. Treatment includes glucocortocoids (GC) in addition to other immunologic agents. We present, to our knowledge, the first case of ANCA-negative crescentic glomerulonephritis associated with sweet syndrome. Case Description: A 52 y/o male presented with new onset weakness and painful skin rash. His autoimmune and malignancy work up were negative. A diagnosis of SS was established based on skin biopsy. Treatment comprised of GC with a 9-week taper. Four months later, he presented with fever, nausea, and vomiting. His serum creatinine was elevated to 4.48 mg/dL from a baseline of 1.2 mg/dL. Urinalysis showed proteinuria and hematuria. Kidney biopsy revealed pauci-immune necrotizing glomerulonephritis with crescents. Despite negative ANCA serology, treatment mimicked that of AAV, involving GC and rituximab, resulting in renal function and proteinuria improvement. Discussion: Although association of SS with AAV has been previously reported, we present the first case of such association with ANCA-negative vasculitis. Treatment with GC and rituximab resulted in improvement of acute kidney injury and proteinuria, suggesting that similar immunosuppressive regimen may be efficacious regardless of the ANCA status.H&E stain (top L) and PAS stain (top R) Active segmental necrotizing lesion with cellular crescents. IMF (Bottom L) pseudo-linear IgG staining. EM (Bottom R) Thickened GBM with no immune deposits