Intravenous sodium thiosulfate for treating tumoral calcinosis associated with systemic disorders: Report of four cases.

Intravenous sodium thiosulfate (ivSTS) is a promising new therapeutic option for calciphylaxis related to end-stage renal disease. However, its effect on tumoral calcinosis (TC) complicating autoimmune connective-tissue diseases has been scarcely described. We report here 4 cases (3 adults and 1 child) of TC treated with ivSTS. TC was secondary to CREST syndrome, dermatomyositis (1 adult and 1 child) and systemic erythematous lupus and involved multiple sites in all cases. In all 4 patients, TC was responsible for joint pain, reduced mobility, inflammatory flares and skin fistulations. One patient experienced difficulty sitting due to the pain induced by calcified lesions on the buttock; another patient had major disability, moved only with wheelchair and was under opioid treatment for pain. For all patients, treatment with several medications before STS was unsuccessful. The 3 adults received at least 6 cycles of ivSTS (20g/d, 5 days/month) and the child received a daily infusion of 17g STS during 1 month then a 9-g/d infusion during 3 months. Two adults and the child showed clinical improvement with STS treatment and the third adult felt disappointed and stopped STS treatment after 6 months. The child also stopped STS after 6 months due to vomiting. In one patient, an intensive regimen of ivSTS (20g every 2 days) controlled recurrent flares and fistulations. Unfortunately, TC remained unchanged. Further studies are needed to decipher how STS modulates ectopic calcification, the optimal regimen and posology.