A Study Evaluating the Efficacy, Safety, Pharmacokinetics and Pharmacodynamics of Crovalimab in Pediatric Participants With Atypical Hemolytic Uremic Syndrome (aHUS)

Inclusion Criteria: * Body weight \>= 5 kg at screening. * Vaccination against Neisseria meningitis serotypes A, C, W, and Y; vaccination against serotype B, according to national vaccination recommendations. * Vaccination against Haemophilus influenzae type B and Streptococcus pneumoniae, according to national vaccination recommendations. * For patients continuing to receive other therapies concomitantly with crovalimab (e.g., immunosuppressants, corticosteroids, mammalian target of rapamycin inhibitor (mTORi), or calcineurin inhibitors): stable dose for \>=28 days prior to screening and up to the first crovalimab administration. * For female participants of childbearing potential: an agreement to remain abstinent or use contraception. * Participants with a prior kidney transplant are eligible if they have a known history of complement-mediated aHUS prior to the kidney transplant. * Onset of initial TMA presentation within 28 days prior to the first dose of crovalimab (for Naive Cohort only). * Documented treatment with either eculizumab or ravulizumab (for Switch Cohort only). * Clinical evidence of response to a C5 inhibitor (for Switch Cohort only). * Poorly controlled TMA following treatment with another C5 inhibitor (for C5 SNP participants in the Pretreated Cohort only). * Known C5 polymorphism (for C5 SNP participants in the Pretreated Cohort only). Exclusion Criteria: * TMA associated with non-aHUS related renal disease. * Positive direct Coombs test. * Chronic di…