GALNS and mucopolysaccharidosis type 4A: Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is an inherited, autosomal recessive disease caused by a deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS), which results in excessive lysosomal storage of keratan sulfate (KS) and chondroitin 6-sulfate (C6S) in many tissues and organs.