SummaryCalciphylaxis, also referred to as calcific uremic arteriolopathy, is a relatively rare but well described syndrome that occurs most commonly in patients with late stage CKD. It is characterized by very painful placques or subcutaneous nodules and violaceous, mottled skin lesions that may progress to nonhealing ulcers, tissue necrosis, and gangrene with a 1-year mortality rate >50%. The pathogenesis of calciphylaxis is poorly understood. Risk factors include female sex, obesity, hyperphosphatemia, hypercalcemia, hyperparathyroidism, longer dialysis vintage, hypercoagulable states, and use of calcium-containing phosphate binders and warfarin. Treatment strategies for calciphylaxis are limited by inadequate understanding of its pathophysiology. Therapy is generally focused on correcting disturbances of calcium, phosphorus, and parathyroid hormone metabolism. Additional therapy focuses on decreasing inflammation and on dissolution of tissue calcium deposits with sodium thiosulfate and/or bisphosphonates. Successful treatment generally results in improvement of pain and healing of the lesions within 2-4 weeks, but the disorder generally takes many months to completely resolve.Clin J Am Soc Nephrol 9: 166-173, 2014. doi: 10.2215/CJN.00320113Case Description Abhijit Naik, MD (Renal Fellow). A 54-year-old white man was referred from an outside dialysis clinic for evaluation of necrotic skin lesions. He had a 10-year history of diabetes and hypertension, with ESRD secondary to diabetes. His history was also significant for coronary artery disease, with two prior myocardial infarctions and atrial fibrillation. He had been undergoing thrice-weekly hemodialysis for 2 years with a Kt/V between 1.3-1.4. Three months before presentation he noticed several small firm and very painful nodules on both anterior thighs. He stated that after several weeks the lesions became much larger, black, and spread to the lateral thighs and buttocks. He was treated with mupirocin ointment and a vascular evaluation revealed normal blood flow in his legs. Aside from these painful lesions, he stated that he generally felt "ok." Dialysis had been proceeding without problems. He denied chest pain, dyspnea, abdominal pain, or any gastrointestinal complaints. Review of systems was otherwise unremarkable. He never smoked and drank alcohol very infrequently. Medications included aspirin, amiodarone, simvastatin, famotidine, glipizide, clopidogrel, sevelamer carbonate, hydrocodone, and gabapentin. He had no known allergies.On examination his vital signs were as follows: temperature, 98.8°F; heart rate, 80 beats per minute; BP, 94/60 mmHg, with no orthostatic changes; and respiratory rate, 20 breaths per minute. His BP was generally low, with systolic BP averaging between 90 and 100 mmHg. He was an ill appearing male in mild distress from extremity pain. His lungs were clear and a cardiovascular examination revealed a regular rate and rhythm with a 2/6 holosystolic murmur. His abdomen had normal bowel sounds and was mildly distended with some asc...