This Phase IV post-marketing, non-interventional, open label, non-comparative and prospective study will examine the efficacy and safety of rituximab in participants who had previously received rituximab in terms of everyday medical practice. Efficacy and safety of rituximab will be determined 24 weeks after receiving the first infusion, 24 weeks after the second infusion repeated courses of treatment (if the participants receive another course of rituximab) and 24 weeks after the third infusion repeated courses of treatment (if the participants receive third course of rituximab). Protocol does not specify the criteria for initiation of treatment with rituximab and procedure of the infusion of rituximab. Rituximab will be administered at the discretion of treating physician according to approved label.