GALNS, also known as N-acetylgalactosamine-6-sulfatase, is an enzyme-encoding gene essential for the breakdown of glycosaminoglycans, specifically keratan sulfate and chondroitin 6-sulfate [1,2,3,4,5,6,7]. Its normal function is crucial for the metabolism of these substances, and its role is associated with maintaining normal skeletal and connective tissue health [1,2,3,4,5].

Mutations in the GALNS gene lead to mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome), an autosomal recessive lysosomal storage disorder [1,2,3,4,5,6,7]. In patients with MPS IVA, the deficiency of GALNS enzyme activity causes the accumulation of glycosaminoglycans in lysosomes, resulting in pleiotropic disease manifestations, mainly characterized by severe skeletal dysplasia, which can lead to significant disability by the second decade of life [1,2,3,4,5,7]. The mutation spectrum of GALNS is diverse, including missense, nonsense, splicing, small frameshift deletions/insertions, intronic, and large del/ins and complex rearrangements [1]. Genotype-phenotype correlations have been studied, with most patients with at least one GALNS null variant presenting a severe phenotype, and missense variants mapped to different residues of the GALNS protein resulting in different phenotypes [3].

In conclusion, GALNS is essential for the normal metabolism of glycosaminoglycans, and its malfunction due to genetic mutations is closely associated with MPS IVA. Understanding the function of GALNS through the study of MPS IVA patients and associated genetic mutations helps in accurately diagnosing the disease, providing genetic counseling, and exploring potential treatment strategies such as enzyme replacement therapy [1,2,3,4,5,7].