MPS IVA results from an alteration of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) (EC 3.1.6.4) enzyme activity secondary to biallelic pathogenic variants in GALNS leading to the accumulation of keratan sulfate (KS) and chondroitin-6-sulfate (C6S) in various tissues, resulting in characteristic skeletal and connective tissues abnormalities [4]. Here, GALNS is linked to mucopolysaccharidosis type 4A.