Observational Study to Evaluate Allogeneic HSCT Outcomes for Cerebral Adrenoleukodystrophy (CALD)

Inclusion Criteria: 1. Provide informed consent from a competent custodial parent or guardian with legal capacity to execute a local Institutional Review Board (IRB)/Independent Ethics Committee (IEC) approved consent. In addition, informed assent will be sought from capable subjects, in accordance with the directive of the institution's IRB/IEC and all other local requirements. 2. Be male and ≤17 years of age at the time of treatment, for retrospective and partial prospective/retrospective subjects, or at the time of parental/guardian consent and, where appropriate, subject assent, for prospective subjects. 3. Have a confirmed diagnosis of CALD as defined by abnormal VLCFA profile and cerebral lesion on brain MRI. 4. Depending on the cohort, the subject must: * Be scheduled for allo-HSCT evaluation at a study site (prospective cohort only), * Have received an allo-HSC infusion and be consented in time to complete the Month 24 Visit on study (partial prospective/retrospective cohort only), or * Have received their most recent allo-HSC infusion on or after January 1, 2013 (retrospective cohort only). Exclusion Criteria: 1. Previous treatment with a gene therapy product. 2. Receipt of an experimental transplantation procedure.