Key Inclusion Criteria:  Ability of the participant and/or his/her legally authorized representative (e.g., parent or legal guardian), as appropriate and applicable, to understand the purpose and risks of the study, to provide informed consent, and to authorize the use of confidential health information in accordance with national and local privacy regulations. Genetically confirmed 5q-SMA. Age < 18 years at enrollment.  Key Exclusion Criteria:  Unable or unwilling to provide informed consent. Other types of SMA (non 5q-SMA).  NOTE: Other protocol defined inclusion/ exclusion criteria may apply.