Abstract Background Metachromatic leukodystrophy (MLD), a relentlessly progressive and ultimately fatal condition, is a rare autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme arylsulfatase A (ARSA). Historically management has been palliative or supportive care. Hematopoietic stem cell transplantation is poorly effective in early-onset MLD and benefit in late-onset MLD remains controversial. Hematopoietic stem cell gene therapy, Libmeldy (atidarsagene autotemcel), was recently approved by the European Medicines Agency for early-onset MLD. Treatment...