GALNS and mucopolysaccharidosis type 4A: In MPS-IVA/B (Morquio syndrome), deficiency in the galactose 6 sulfate sulfatase (GALNS) and/or β-galactosidase (Figure 1) impairs the further steps of KS catabolism, which results in abnormal KS and C6-S levels in tissues [71,72].