Morquio syndrome is a rare inherited birth defect that is estimated to occur in one of every 200,000 births. The disease may not be visible at birth; symptoms usually begin between ages 1 and 3. Morquio syndrome is a progressive disease, meaning symptoms get worse as a child grows. Morquio syndrome is part of a group of diseases called mucopolysaccharidosis (MPS). Morquio is also known as MPS IV.