This study is being conducted to explore the potential benefits of a twelve-month doxycycline (at the best tolerated dose of 200 mg/day) and tauroursodeoxycholic acid (750 mg/day) treatment on disease progression in patients affected by transthyretin amyloidosis, including: 1) patients not eligible for liver transplantation; 2) patients eligible for liver transplantation, as a "bridge" therapy between the time of diagnosis and surgery, with the aim of stabilizing the disease; 3) patients showing disease progression after liver transplantation performed since at least 1 year.