Multicenter pharmacological observational prospective, no-profit, study. This study was designed to get a real-life snapshot across several Italian Hepatology centers. All HDV patients are followed up according to EASL 2017 guidelines. This allows uniformity on the indication for antiviral treatment and management of that antiviral therapy. No off-label medications are used. All data are retrievable from the patient's medical record. In addition, clinical and biochemical data from patients at month 0, 1, 2, 4, 6 and 12 of treatment, and otherwise within the study period, will be collected longitudinally. The primary objective of the study is to describe the virological response to BLV in all patients starting BLV therapy for CHD, defined as a \>2 Log decline in HDV-RNA or undetectable HDV-RNA (using the Robogene 2.0 quantitative kit, LLQ \<6 IU/ml) at month 12 of therapy. HDV patients who will start therapy with BLV 2 mg/day from May 2023, according to AIFA guidelines, will be consecutively enrolled.