Ectopic calcification and ossification complicate many diseases, which are rare for the most part. These calcifications (or ossifications) are generally classified according to their apparent formation mechanism. Even if very different diseases can be at the origin, these calcifications (or ossifications) have as common points: an unknown physiopathology, a composition of calcium pyrophosphate for the most part and l no curative treatment validated to date.

Indeed, although several reported cases suggest the potential efficacy of different treatments , none of these treatments is currently recognized as effective because of the absence of confirmation data or because of contradictory results.

Sodium thiosulfate (STS) has been used for a long time as an antidote to cyanide poisoning and as a protective agent against cytotoxic side effects such as ifosphamide. More recently, STS has been reported in the treatment of renal calcification. vascular or even subcutaneous. First prospective studies on animal models and in humans seem to confirm the interest of this product in the treatment of these abnormal calcifications.

For several months, a magistral preparation in the form of ointment based on STS has been developed by the pharmacy of Limoges University Hospital in order to combine the local effect of STS while avoiding the side effects of an administration of this treatment by systemic way. The first uses of this preparation appear promising and some preliminary results have already been published. The benefit / risk ratio of this approach seems to be advantageous for clinicians since preparations whose composition is close are currently validated by the FDA and the World Health Organisation for the treatment of benign pathologies such as cutaneous dermatophytes or pityriasis versicolor.

Inclusion Criteria:

• any patient treated with sodium thiosulfate dermally provided by the pharmacy of Limoges University Hospital.
• availability of an objective imaging evaluation to compare the volume or surface of calcifications (or ossifications) treated (on two orthogonal incidences) before and after 6 months of treatment application.
• consent to participation in the study signed by the patient or by one of the holders of parental authority in the case of a minor patient.

Exclusion Criteria:

• calcification with concomitant cutaneous rupture which can allow an externalization of the calcium material by mechanical effects.
• Patient with calcification secondary to one of the following pathologies:
• diabetes
• chronic renal failure
• iatrogenic origin

patient with ectopic calcification / ossification