GALNS and mucopolysaccharidosis type 4A: In MPSIVA patients, the deficiency of GALNS results in progressive pathological accumulation of GAGs keratan sulfate (KS) and chondroitine-6-sulfate (C6S) in several tissues, mainly in the skeletal system, the cartilaginous tissues, cornea and heart valves (Neufeld and Muenzer 2001; Sawamoto et al. 2016; Khan et al. 2017; Melbouci et al. 2018).