This is a prospective, multi center, multinational, non-interventional observational study. All patients will be managed according to the clinical site's normal clinical practice, i.e., the diagnostic and clinical treatment/practice process that a clinician chooses according to their clinical judgement for an SMA patient. Clinical care will not be driven by the protocol. No additional visits or investigations will be performed beyond normal clinical practice. Patients will be followed for 15 years from enrolment or until death, whichever is sooner.