Background:Combination therapy with pegylated interferon, ribavirin and a first-generation NS3/4A protease inhibitor, telaprevir or boceprevir, is the new strategy for treatment of genotype 1 chronic hepatitis C virus infection. This combination improves therapeutic efficacy but it also increases the risk of adverse events.Objective:The aim of the study was to analyze frequency and severity of dermatological adverse events during protease inhibitor-based therapy and to evaluate the risk factors for their development.Patients and methods:This is a retrospective study of 109 patients with genotype 1 chronic hepatitis C treated with boceprevir (n=33) or telaprevir (n=76) based triple therapy. A logistic regression for relationship between clinical, demographic and laboratory factors and cutaneous adverse events was performed.Results:Dermatological adverse events (skin rash, pruritus, anorectal paresthesia) occurred in both treatments (boceprevir and telaprevir) with similar frequency: 28% in telaprevir and 21% in boceprevir. In patients treated with telaprevir, men were more predisposed to develop skin rashes compared to women (OR 4,1 p=0,014) and age above 45 years was associated with occurrence of pruritus in men (OR 8,16 p=0,014). Being a female, coexistence of autoimmune thyroiditis and advanced liver fibrosis were independent factors predisposing to development of anorectal paresthesia (OR 4,13 p=0,041, OR 4,25 p=0,029, OR 4,54 p=0,018 respectively) in this group. In patients treated with boceprevir, coexistence of autoimmune thyroiditis predisposed to skin rashes (OR 10,22 p=0,017) and being a female predisposed to pruritus (OR11,2 p=0,033). The adverse events occurred after a mean time of 8,6 (range 1—24) weeks after initiation of therapy.Conclusions:In patients with chronic hepatitis C who received the triple therapy, the anorectal paresthesias were observed only in patients treated with telaprevir. The predisposing factors for this adverse event were: female gender and advanced liver fibrosis. The risk factors for other dermatological adverse were: 1) being a male over 45 years, for skin rashes and pruritus (for telaprevir), 2) coexistence of autoimmune thyroiditis for skin rashes (for boceprevir), 3) being a female, for pruritus (for boceprevir).