In treatment of digital ulcers in patient with SSc: - intravenous iloprost - PDE-5 inhibitors To prevent development of new digital ulcers in SSc: - PDE-5 inhibitorTo reduce the number of new digital ulcers in SSc, especially in patients with multiple digital ulcers despite use of calcium channel blockers, PDE-5 inhibitors or iloprost therapy: - Bosentan. The gene discussed is PDE5A; the disease is systemic sclerosis.