GALNS and mucopolysaccharidosis type 4A: GAGs, such as keratan sulfate and chondroitin 6-sulfate, are macromolecules that accumulate at the intracellular level, predominantly in specific tissues [11,12], the extracellular matrix of hyaline cartilage and connective tissues, cardiac valves, the cornea, etc. Currently, the two available therapies for MPS IVA in clinical practice are intravenous administration of the recombinant GALNS enzyme [13,14,15], (elosulfase alfa) to patients weekly (so-called enzyme replacement therapy (ERT)) and hematopoietic stem cell transplantation.