In MPS IVA the deficient enzyme, N‐acetylgalactosamine 6‐sulphatase (GALNS), is responsible for hydrolysing N‐acetyl‐D‐galactosamine 6‐sulfate residues within chondroitin 6‐sulfate (CS), as well as de‐sulphating galactose 6‐sulfate residues present in keratan sulfate (KS).2 The gene discussed is GALNS; the disease is mucopolysaccharidosis type 4A.