This study is about a medicine called crovalimab and aims to see how well it works and how safe it is for people with a condition called atypical Hemolytic Uremic Syndrome (aHUS), which affects the blood and kidneys. To join, participants need to be vaccinated against certain diseases like Neisseria meningitidis and Haemophilus influenzae. Some people who have had a kidney transplant can also join if they have a history of aHUS. Participants will need regular check-ups and meet specific health requirements, like not having active infections or certain other diseases. The study will not accept people on chronic dialysis or those with certain types of infections. The study will help understand how the body handles crovalimab and how it affects the disease.

• Participants will receive crovalimab and may continue using other stable medications.
• Participants must follow certain health guidelines, like staying free from certain infections.
• Those joining can receive a structured health evaluation and treatment plan.