A Rare Case of Nonuremic Calciphylaxis in a Patient with Mild Macroalbuminuric CKD

Introduction: Nonuremic calciphylaxis (NUC) is a rare, poorly understood entity that can occur in patients without end-stage kidney disease (ESKD) and kidney transplantation. Sparse data has shown several risk factors associated with NUC, but these associations are not well understood. We present a case of NUC in a patient with mild macroalbuminuric chronic kidney disease (CKD G2A3). Case Description: A 61-year-old female with long-standing uncontrolled type 2 diabetes, peripheral vascular disease, hypertension, coronary artery disease, uterine cancer status post total hysterectomy, hypothyroidism, and mild macroalbuminuric chronic kidney disease (CKD G2A3, eGFR 70-80 ml/min/1.73 m2, BUN 18, UACr 749 mg/g) who presented with a painful, ulcerated skin lesion on her right leg following mild trauma. She was evaluated by vascular surgery and underwent angioplasty of the right peroneal artery and anterior tibial arteries. Despite angioplasty, the ulcerated lesion did not improve, and she was referred to a dermatologist. Subsequently, a skin biopsy was performed which showed acute ulceration with necrosis and inflammatory exudate with associated dermal sclerosis and vascular peri-eccrine calcifications concerning for atypical nonuremic calciphylaxis. Calcium, phosphorus, and PTH levels (77 pg/ml) were within normal limits. She was taking vitamin D supplementation for many years and her vitamin D-25-OH was elevated to 72 ng/ml, which was stopped. Serologies were only notable for an elevated rheumatoid factor. She was started on sodium thiosulfate which led to improvement in the skin lesion and pain. Discussion: Calciphylaxis is typically seen in patients with ESKD and kidney transplantation. However, it has rarely been described in patients with nonuremic causes. It is important to report these cases to better understand the risk factors associated with NUC. Our patient had mild CKD, vitamin D deficiency, uterine cancer, uncontrolled type 2 diabetes, peripheral artery disease, elevated rheumatoid factor, and was on dual anti-platelet therapy. All of these are proposed triggers for NUC. There is currently no standard treatment for NUC, but sodium thiosulfate has shown promise, was trialed in this patient, and led to clinical improvement.