Clinical Image: Periarticular nodules in a patient with renal failure

A 25-year-old man with a history of immunoglobulin A nephropathy resulting in end-stage kidney disease on peritoneal dialysis presented with soft tissue masses over several joints. Six months ago, he developed sudden pain in left wrist with subsequent soft tissue mass formations. On examination, he had many periarticular nodules in the fingers and toes. X rays showed extensive bilateral soft tissue calcification in a periarticular pattern. Dual-energy computed tomography showed periarticular erosion of distal interphalangeal and numerous positively birefringent soft tissue calcifications. Excision of a lesion showed dystrophic calcification in the skin. Laboratory evaluation was notable for normal uric acid 4.9 mg/dL, calcium 8.1 mg/dL, phosphorus 12.8 mg/dL (high), and parathyroid hormone 492 pg/mL (high). This case illustrates calcinosis of chronic renal failure characterized by dystrophic calcium phosphate crystal deposits related to high calcium phosphorus product (Ca × P) commonly >70 mg/dL. Clinical manifestations may mimic crystalline arthropathy such as tophaceous gout or calcium pyrophosphate disease, or soft tissue deposits resulting in pain, ischemia, ulceration, or arteriolopathy, commonly termed calciphylaxis. Risk factors include end-stage kidney disease, longer time on dialysis (hemodialysis or peritoneal), hyperparathyroidism, diabetes, obesity, glucocorticoid use, chronic inflammatory diseases, warfarin use, female sex, protein C/S deficiency, hypervitaminosis D, and aluminum intoxication. Treatment is aimed at lowering Ca × P by dietary restriction of calcium and phosphorus, chelation using non–calcium-based phosphate binders, sodium thiosulfate, removal with hemodialysis either by intensification or using a low calcium dialysate, or parathyroidectomy in patients with hyperparathyroidism. Sodium thiosulfate works as a chelator, vasodilator, and antioxidant and can be given in many formulations and dosing regimens, including intravenous (12.5 g to 25 g, 2 to 5 times per week per month dosed at the end of dialysis sessions, total dose of 50 g to 125 g per month as needed), intralesional/intradermal (40 mg/mL to 150 mg/mL, 0.1 mL/cm2, given monthly as needed in the office), and, less commonly, at-home regimens of oral (1 g to 8 g daily) or topical (3%–10%) administration. Efficacy is highly variable and dependent on individual factors, but intravenous administration is reported with higher success. Peritoneal dialysis historically confers a higher risk than hemodialysis, and intensifying hemodialysis by increasing duration or frequency can effectively lower Ca × P, along with a using a low calcium dialysate (2.5 mEq/L). This patient had a high Ca × P of 104 mg/dL with extensive destructive calcinosis, so he was given one course of intravenous sodium thiosulfate and switched from peritoneal dialysis to hemodialysis with resolution. Disclosure form Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.