This study investigates cold agglutinin disease (CAD) and cold agglutinin syndrome (CAS) through a multinational, observational, prospective, longitudinal registry. CAD and CAS are conditions where the body's immune system mistakenly targets and destroys its own red blood cells, leading to anemia. This registry aims to collect data to better understand these conditions and their treatment outcomes.

Participants in this study will have their health data collected as part of routine care. This study does not involve any changes to the participants' treatment plans. The registry will include a specific focus on a cohort of patients treated with an investigational medication. An observational study is a type of research study where data is collected by observing participants receiving routine care, without changing their treatment, which may focus on people using specific medications or having certain conditions to better understand how treatments work.

• Who can participate: Adults aged 18 years and older with a diagnosis of CAD or CAS can participate. Individuals with mixed warm and cold autoimmune hemolytic anemia or those currently in an interventional trial are not eligible.
• Study details: Participants will have their health data collected as part of routine care without changes to their treatment. This observational study focuses on understanding CAD and CAS by tracking patient outcomes over time.