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Warfarin-Associated Nonuremic Calciphylaxis. Importance: Classic calciphylaxis associated with renal failure is a life-threatening disease. Warfarin-associated calciphylaxis without renal injury has been described, but whether it is a subset of classic calciphylaxis or a different entity remains unknown. We describe 1 case of warfarin-associated calciphylaxis, present data from 2 others from our institution, and review all cases of warfarin-associated calciphylaxis available in the literature. Our review indicates that warfarin-associated calciphylaxis is clinically and pathophysiologically distinct from classic calciphylaxis. Objective: To review warfarin-associated calciphylaxis and determine its relationship to classic calciphylaxis. Design, Setting, and Participants: We searched MEDLINE and Ovid without language or date restrictions for case reports of calciphylaxis from the inpatient setting using the terms "calciphylaxis and warfarin," "non-uremic calciphylaxis," and "nonuremic calciphylaxis." We defined nonuremic calciphylaxis as a histopathologic diagnosis of calciphylaxis without severe kidney disease (serum creatinine level >3 mg/dL; glomerular filtration rate <15 mL/min; acute kidney injury requiring dialysis; and renal transplantation). Exposures: Each patient had been exposed to warfarin before the onset of calciphylaxis. Main Outcomes and Measures: Patient data were abstracted from published reports. Original patient medical records were requested and reviewed when possible. Results: We identified 18 patients with nonuremic calciphylaxis, 15 from the literature, and 3 from our institution. Patients were predominantly female (15 of 18 [83%]) with ages ranging from 19 to 86 years. Duration of warfarin therapy prior to calciphylaxis onset averaged 32 months. Lesions were usually located below the knees (in 12 of 18 [67%]). No cases reported elevated calcium-phosphate products (0 of 17 [0%]). Calcifications were most often noted in the tunica media (n = 8 [44%]) or in the vessel lumen and tunica intima (n = 7 [39%]). The most common treatments included substitution of heparin or low-molecular weight heparin for warfarin (n = 13 [72%]), intravenous sodium thiosulfate (n = 9 [50%]), and hyperbaric oxygen (n = 3 [17%]). The survival rate on hospital discharge was remarkably high, with 15 cases (83%) reporting full recovery and 3 cases ending in death. Conclusions and Relevance: Warfarin-associated calciphylaxis is distinct from classic calciphylaxis in pathogenesis, course, and, particularly, outcome. This finding should influence clinical management of the disease and informs targeted treatment of the disease.