GALNS and mucopolysaccharidosis type 4A: Mucopolysaccharidosis type IVA (MPS 4A), also known as Morquio (Morquio-Brailsford) syndrome results from the accumulation of keratan sulfate (KS) and chondroitin-6-sulfate (C6S), whereas the primary cause is mutations in the gene encoding N-acetyl-galactosamine-6-sulfatase (GALNS).