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An ESRD patient on CAPD was recently admitted to our hospital with possible pneumonia. It was noticed that he had painful plaque-like necrosis, with areas of ulceration. Even in the absence of a skin biopsy, the consensus was that he had calciphylaxis based on gross appearance alone and as a result, he was started on intravenous Sodium Thiosulfate 5g three times weekly.

Calciphylaxis (or calcific uremic arteriolopathy) is an uncommon but dreaded complication of renal failure characterized by painful nodular or plaque-like subcutaneous calcification often leading to ischemia, necrosis, ulceration and secondary infection. Calciphylaxis mostly occurs in patients with ESRD receiving hemo- or peritoneal dialysis although it is known to occur also in patients with CKD. Well described risk factors include female sex, hyperphosphatemia, hypercalcemia, hyperparathyroidism, the use of Ca-containing phosphate binders, vitamin D, and hypercoagulable states.

The diagnosis usually is made easily by characteristic clinical, bone scan and x-ray findings of well-defined tumor-like masses of Ca. (see previous posts)

Treatment recommendations have included reduction of serum Ca and P (and the CaxP product) by the use of low Ca dialysis baths, cessation of Ca-containing phosphate binders and vitamin D supplements, use of sevelamer, and possibly parathyroidectomy in refractory cases. Several case reports have reported the successful treatment of calciphylaxis with Sodium Thiosulfate. Sodium thiosulfate pentahydrate (Na2S2O3) has a molecular weight of 248. It distributes throughout extracellular fluids and is normally is excreted unchanged in the urine. It has been used as antidote for acute cyanide poisoning and as a topical treatment for acne and pityriasis versicolor. The theory is that sodium thiosulfate inhibits the precipitation of Ca salts and also leads to dissolution of Ca deposits into a more soluble form (Ca thiosulfate salts). The treatment is required for up to 4-12 months although a reduction of pain is usually seen within a couple of weeks. The main side effect is an anion gap metabolic acidosis that is related to the retention of sulfate salts. It has been suggested that patients who develop this complication can be treated with a high bicarbonate dialysis.

Back to our patient, we increased the dose of sodium thiosulfate to 25g. After 2 weeks treatment, the patient was tolerating the medication well and reported a significant improvement both in the pain, and in the necrotic lesions.

Posted by Tarek Alhamad

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