• Total number of new DUs per patient observed by the investigator at planned visits (a patient diary will be used to record DUs that might appear and disappear between two planned visits) [ Time Frame: At planned visits ] [ Designated as safety issue: No ]
  
• Time to complete healing of each baseline DU [ Time Frame: Baseline to healing ] [ Designated as safety issue: No ]
  
• Time to complete healing of each new DU [ Time Frame: New DU occurence to healing ] [ Designated as safety issue: No ]
  
• 16 weeks in the Scleroderma Health Assessment Questionnaire (SHAQ) and in the composite of hand components of the SHAQ: grip, hygiene, dressing and grooming [ Time Frame: 16 weeks ] [ Designated as safety issue: No ]
  
• 16 weeks in overall hand pain related to finger ulcers [ Time Frame: 16 weeks ] [ Designated as safety issue: No ]
  
• 16 weeks in UK SSc Functional Score (UKFS) [ Time Frame: 16 weeks ] [ Designated as safety issue: No ]
  

• Adverse events up to 24 hours after last study medication [ Time Frame: Up to 24 hours after last study medication ] [ Designated as safety issue: Yes ]
  
• Serious adverse events up to 28 days after last study medication [ Time Frame: Up to 28 days after last study medication ] [ Designated as safety issue: Yes ]
  
• AEs leading to permanent discontinuation of the study medication [ Time Frame: Time to AE leading to permanent DC ] [ Designated as safety issue: Yes ]
  

Inclusion Criteria:

• · Patients with SSc according to the classification criteria of the American College of Rheumatology

  • SSc patients with at least one DU at baseline qualifying as a CU (see definition section 3.2.2)
  • CU occurred < 3 months and > 1 week prior to randomization The subset of patients with SSc felt to be at high risk for DUs will be identified in the screening period but will not be eligible for enrollment until a CU has developed.
  • Male or female patients ³ 18 years of age
• Women of childbearing potential must have a negative pre-treatment pregnancy test and use a reliable method of contraception during study treatment and for at least 3 months after study treatment termination.

• Women not of childbearing potential are defined as postmenopausal (i.e., amenorrhea for at least 1 year), or surgically or naturally sterile.

  • Signed informed consent

Exclusion Criteria:

• · DUs due to condition other than SSc

  • Severe PAH (WHO class III and IV)
  • Systolic blood pressure < 85 mmHg.
  • Hemoglobin concentration < 75% of the lower limit of the normal range
  • AST and/or ALT values greater than 3 times the upper limit of normal
  • Moderate to severe hepatic impairment, i.e., Child-Pugh Class B or C
  • Severe malabsorption or any severe organ failure (e.g., lung, kidney) or any life-threatening condition
  • Pregnancy or breast-feeding
  • Previous treatment with bosentan
  • Treatment with any of the following: glibenclamide (glyburide), fluconazole, cyclosporine A, tacrolimus and any other calcineurin inhibitor 1 week prior to randomization
  • Local injection of botulinum toxin in an affected finger 1 month prior to randomization
  • Treatment with parenteral prostanoids (prostaglandin E, epoprostenol, treprostinil sodium or other prostacyclin analogs) 3 months prior to randomization
  • Treatment with inhaled or oral prostanoids one month prior to randomization
  • Systemic antibiotics to treat infection of DUs 2 weeks prior to randomization
  • Treatment with phosphodiesterase inhibitors such as sildenafil, except for intermittent treatment of male erectile dysfunction
  • Body weight < 40 kg
  • Patient with conditions that prevent compliance with the protocol or adhering to therapy
  • Patient who received an investigational product within 1 month preceding screening
  • Known hypersensitivity to bosentan or any of the excipients