Sildenafil Effect on Digital Ulcer Healing in sClerodErma SEDUCE STUDY

Inclusion Criteria: * Patient with systemic sclerosis (ScS) according to the classification criteria of the American College of Rheumatology or of "LeRoy" and "Medsger". * ScS patient with at least one ongoing ischaemic hand digital ulcer at baseline (see below the eligibility conditions of a digital ulcer). * Patient must have provided written informed consent prior to enrolment. Patient agrees to come to the follow up visits inside the protocol specified range. * Relative to each DU: DU must be beyond the proximal interphalangeal joint, on finger surface, of ischemic origin according to the physician, and not over subcutaneous calcifications or bone relief. Exclusion Criteria: * PAH requiring PDE5 inhibitors or prostacyclin history of stroke, myocardial infarction or life threatening arrhythmia within the last 6 months * severe cardiac failure (NYHA IV) or unstable angina within the last 6 months. * hereditary degenerative retinal disorders non-arteritic anterior ischemic optic neuropathy or untreated proliferative diabetic retinopathy * uncontrolled diabetes mellitus * Patient with known severe lung obstructive disease (FEV1\<70% on last available pulmonary function tests). * severe hepatic impairment * Patient with known impairment of renal function (serum creatinine \> 2.5 ULN). * Patient with severe malabsorption or any severe organ failure (e.g., lung, kidney) or any life-threatening condition. * Patient who has had surgical sympathectomy performed in the previous 12 months. * Patient with a history of upper extremity deep vein thrombosis or lymphedema within the previous 3 months. * Patient participating in a clinical trial or having participated in a clinical trial within the previous 3 months. * Patient having received a treatment with sildenafil for digital ulcers or pulmonary arterial hypertension within 3 months prior to inclusion. * Patient having received a treatment with parenteral prostanoids (prostaglandin E, epoprostenol, treprostinil sodium or other prostacyclin analogs) within 3 months prior to inclusion. * Patient having received a treatment with inhaled or oral prostanoids one month prior to inclusion. * Patient with previous intolerance or allergy to PDE5 inhibitors or a history of multiple clinically significant allergies. * Pregnant or lactating female. * Patient with uncontrolled tachyarrhythmias or bradyarrhythmias, or placement of pacemaker or implantable defibrillator within 60 days prior to randomization. * Patient with hemodynamic instability or systolic arterial pressure less than 90 mmHg and/or symptomatic orthostatic hypotension. * Patient receiving all forms of prostacyclin or nitrates or nitric oxide donors in any form including Nicorandil. * Patient receiving potent inhibitors of CYP3A4 such as ketoconazole, itraconazole, ritonavir. * Patient with any condition that prevents compliance with the protocol or adhering to therapy. * Patient who has donated blood during the previous month or intends to donate blood or blood products during the study or for one month following completion of the study. * Patient under guardianship (including curators) or deprived of liberty. * Patient presenting with an anatomic malformation of penis (such as an angulation, sclerosis of erectile tissue or "Lapeyronie's disease"). * Patient presenting with a disease which predisposes to priapism (such as sickle-cell disease, myeloma or leukemia). * Patient presenting with at least one digital ulcer meeting the exclusion criteria (see below). * Relative to each DU: * Digital ulcer due to conditions other than scleroderma. * Non ischaemic digital ulcer. * Infected digital ulcer requiring systemic antibiotherapy. * Digital ulcer requiring urgent surgery.