Morquio syndrome is an autosomal recessive mucopolysaccharidosis characterized by short trunk dwarfism, fine corneal opacities, skeletal changes, and normal intelligence. Morquio syndromes A (MPS4A; 253000) and B (MPS4B; 253010) are caused by mutations in the N-acetylglucosamine-6-sulfate sulfatase (GALNS; 612222) and beta-galactosidase (GLB1; 611458) genes, respectively. MPS4A and MPS4B are characterized biochemically by increased urinary excretion of keratan sulfate (Beck et al., 1986). There is some evidence of an additional form of Morquio syndrome, referred to here as type C, in which urinary excretion of keratan sulfate is absent. However, McKusick (1972) suggested that the nonkeratosulfate- excreting Morquio syndrome may be allelic to other forms of Morquio syndrome.