Background/Purpose: Calcinosis is a common complication of systemic sclerosis (SSc), though effective treatment options are limited. Of the several medical therapies that have been employed over the years, chelation with intravenous ethylenediaminetetraacetic acid (EDTA) has shown subjective and objective improvement, but its use has been limited by side effects, such as tetany, hypocalcemia, and kidney dysfunction. Using a slower rate of intravenous (IV) administration, toxicity was less frequently demonstrated in animal models. The objective of this project was to evaluate the safety and efficacy of EDTA in a case series of patients with SSc associated calcinosis.

Methods: Out of 34 identified patients with SSc associated calcinosis as defined by the 2013 ACR/EULAR classification criteria, three accepted the invitation to receive EDTA. These patients had clinical and radiographic evidence of one or more calcinotic deposits in either the trunk or the upper or lower extremities. Patients received EDTA chelation infusion (1.5gm EDTA in 500ml total volume IV) once weekly for total of 12 weeks. Radiographs of calcinotic burden were monitored prior to treatment and at 12 weeks. The primary endpoint was the percentage of patients without radiographic progression of calcinosis at 12 weeks. Key secondary endpoints included the completion of an unvalidated Mawdsley Calcinosis Questionnaire (MCQ) per permission of Dr. Saketkoo (1), and important safety signals, which included monitoring of renal function, and serum calcium.

Results: Three female patients with SSc were included, two limited cutaneous SSc and one diffuse cutaneous SSc. The median age was 63 years old. Two patients completed all 12 infusions and 1 patient discontinued therapy after 7 infusions due to financial constraints. No patient experienced clinical or radiographic progression while on therapy. The MCQ survey supported moderate disease burden. One patient reported subjective improvement which was reflected in the MCQ survey results at week 12. Increased 24hr urine calcium excretion was observed in one patient. Due to expected excretion of EDTA in the urine, the urinary calcium post infusion will be an under-estimate. A limitation of the study is that urinary calcium estimate using atomic emission was not done, which would avoid EDTA interference in assessing accurate total urinary calcium excretion. Other secondary endpoints revealed no adverse events occurred.

Conclusion: Low dose EDTA infused at a slow rate was well tolerated. No patients progressed on therapy, one patient reported subjective improvement, and measures of calcium excretion suggested successful chelation in one patient. Larger studies using higher dose of EDTA, are needed to determine the possible benefit of using EDTA to reduce the burden of calcinosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/chelation-therapy-in-the-management-of-calcinosis-associated-with-systemic-sclerosis/