Sodium-Thiosulfate Induced Life-Threatening Metabolic Acidosis Limiting Treatment of Calciphylaxis

BACKGROUND Calcific uremic arteriolopathy (CUA) is a rare and incredibly painful cutaneous disorder secondary to microvascular involvement in which calcium dysregulation leads to stenosis of medium sized arterial blood vessels along with endothelial dysregulation and thrombosis. Ultimately, these patients are at high risk for non-healing wounds with risk of death from sepsis and multi-organ failure. It is a poorly understood condition with limited therapies that do not offer mortality benefit. Prevalence is about 4% in hemodialysis patients. Sodium thiosulfate (STS) can be used in hemodialysis patients but therapy is often limited by the development of high anion gap metabolic acidosis. CASE REPORT A 53-year-old male who had end stage renal disease and who was on hemodialysis and taking warfarin for bio-prosthetic mitral valve replacement and atrial fibrillation presented with non-healing right lower extremity cellulitis which had failed outpatient treatment. A skin biopsy of the lesion was consistent with CUA. The patient failed to improve on calcitriol and cinacalcet and was started on intravenous STS. Subsequently, he developed life threatening metabolic acidosis requiring a bicarbonate drip. He died 12 weeks after his initial diagnosis of CUA. CONCLUSIONS This article seeks to describe how the treatment of CUA; a rare disease with high mortality, is limited by the development of metabolic acidosis when using STS therapy. There is an 80% mortality rate within 6 months from CUA with major adverse effect of a high anion gap metabolic acidosis. Further research is needed in the field of establishing optimal dosing and frequency.