Subcutaneous Injection of Sodium Thiosulfate for Ectopic Calcifications or Ossifications. A Pilot Study

Inclusion Criteria: * Patient presenting with: * ectopic ossification secondary to iPPSD2 or * ectopic calcification secondary to dermatomyositis or * ectopic calcification secondary to systemic sclerosis * Patient aged 2 years or over * Indication of STS infusion validated by a multidisciplinary committee, based on the significant morbidity and/or functional impact of the targeted calcification/ossification * Patient with no planned surgery of the calcifications/ossifications for the twelve coming months * Women of childbearing potential on highly effective contraception (such as hormonal contraception, intrauterine device, intrauterine hormone-releasing system, bilateral tubal occlusion, vasectomised partner or sexual abstinence) * Men with women of childbearing potential partners should use condoms during the whole treatment period and until 91 days after the last injection. * Informed consent signed by the patient / parents * Patient affiliated to the social security system Exclusion Criteria: * Allergy to STS or one of the excipients used * Contraindication to local injection of STS * Anticoagulant therapy * Pregnant, parturient or breastfeeding woman * Patient deprived of freedom by a court judgment or an administrative decision * Patient undergoing psychiatric care under coercion * Legally protected adult patients (guardianship / curatorship) * Patient unable to give consent * Patient placed under judicial protection