The research question and primary aim is to determine if lanthanum carbonate is effective in treating calciphylaxis by measurement of complete or partial remission of skin lesions. Secondary endpoints will be measured to determine if lanthanum carbonate can lower calcium-phosphorus product levels, intact PTH and mortality. Albumin levels will be measured as a marker of nutritional status and inflammation.

Calciphylaxis or calcific uremic arteriolopathy is an infrequently occurring although debilitating vasculopathy seen primarily in patients with end stage renal disease (ESRD) which almost always affects the skin. It has a prevalence rate ~4 % in long term hemodialysis patients, with 1-year survival of 45% and an 8-fold risk of death as compared to the general dialysis population. (Surgery 1997;122:1083-1089, Kidney Int 2001;60:324-332). Despite being described in the literature for over 100 years, there has been no proven effective therapy. Lanthanum carbonate (FOSRENOL®) is a potent non-aluminum, non-calcium phosphate binder that was approved for use to reduce serum phosphate levels in patients with end stage renal disease. Since the proposed etiologic mechanism of injury and vascular calcification of calciphylaxis is predominantly hyperphosphatemia, elevated serum PTH, and hypercalcemia, FOSRENOL® would be an ideal pharmacologic agent to utilize in this extremely enigmatic disease (Dermatol Clin. 2008 Oct;26(4):557-68). Furthermore, a recent case report demonstrated a significant improvement in laboratory parameters and calciphylaxis skin lesions with the use of FOSRENOL® (WMJ. 2008 Nov;107(7):335-8). The primary hypothesis is that since calciphylaxis represents the ultimate sequelae of metastatic vascular calcification predominantly involving hyperphosphatemia, elevated serum PTH, and hypercalcemia, FOSRENOL® will be efficacious in its treatment.

Inclusion Criteria:

• i Participants will have signed a witnessed informed consent. ii Participants will be greater than or equal to 18 years of age iii Chronic renal failure receiving hemodialysis or peritoneal dialysis iv A diagnosis of calciphylaxis proven by skin biopsy or initial dermatology visit within the previous 5 year v Serum phosphorus > 4.5 mg/dL

Exclusion Criteria:

• i Participants are not able to understand or provide written informed consent ii The research team deems that the participant may not be able to follow the study protocol.

iii Non-dependent HD patients receiving dialysis while in acute kidney injury; iv Pregnant dialysis patient v Active gastrointestinal obstruction or bleed vi Active inflammatory bowel disease vii Acute arteriovenous graft occlusion viii Known hypersensitivity to FOSRENOL®