ARSB and lysosomal storage disease: We recently developed a gene therapy approach for mucopolysaccharidosis type VI (MPS VI).9, 10, 11, 12, 13, 14, 15 MPS VI is a rare lysosomal storage disorder (LSD) that is caused by arylsulfatase B (ARSB) deficiency, which results in widespread accumulation and urinary excretion of toxic glycosaminoglycans (GAGs).16