The purpose of the study is to assess skin blood flow after non-invasive local administration of treprostinil by using a low-intensity current (i.e. iontophoresis) on the forearm and the fingers of healthy volunteers and patients with systemic sclerosis. The investigators also aim at assessing the systemic bioavailability and dermal diffusion of treprostinil iontophoresis.

Digital ulcerations are a complication of systemic sclerosis (SSc). Available treatments (i.e. IV iloprost) induce major adverse effects, limiting the use of such therapies. Iontophoresis is a non invasive route of administration of drugs. In experimental and clinical preliminary studies, the investigators have shown that iontophoresis of treprostinil on the forearm of healthy subjects induces a sustained increase in skin blood flux and that it is well tolerated (clinicaltrials.gov NCT01082484, manuscript in press). The investigators therefore aim at validating this proof of concept on the digits of SSc patients.

Inclusion Criteria:

• Cutaneous systemic scleroderma with sclerosed fingers

Exclusion Criteria:

• pregnant or breast-feeding women
• any chronic disease (in the control group)
• smoking