Morquio syndrome, also known as mucopolysaccharidosis type IV (MPS IV), is a rare metabolic disorder that affects the bodys ability to process certain types of sugar molecules called glycosaminoglycans (GAGs) . In Morquio syndrome, the specific GAG that builds up in the body is called keratan sulfate. This birth defect is autosomal recessive and is a type of lysosomal storage disorder.

Patients with Morquio syndrome appear healthy at birth, and the age of onset is usually between 1 and 3 years of age. Morquio syndrome causes progressive changes to the skeleton of the ribs and chest, which may lead to neurological complications such as nerve compression. Patients may also have hearing loss and clouded corneas. Intelligence is usually normal unless a patient has untreated hydrocephalus.

Babies may show little sign of the disease, but as more and more cells become damaged, symptoms start to appear. The condition belongs to a group of diseases called mucopolysaccharidoses (MPSs). MPS IV is also known as Morquio syndrome. There are two forms of Morquio syndrome, A and B, referred to as Morquio A and Morquio B syndrome or MPS IVA and MPS IVB. The two forms are distinguished by the gene product involved; Type A involves a malfunction in the GALNS gene, while Type B involves a malfunction of the GLB1 gene.

The major radiographic features of Morquio syndrome include marked platyspondyly in the thoracic and lumbar spine. The shape of the vertebrae changes from ovoid to ovoid with anterior projection to flat. Odontoid hypoplasia with atlantoaxial instability is typical. Thoracolumbar kyphosis can develop over time and can result in spinal cord compression. The skull is mildly dolichocephalic (elongated) with underdevelopment of mastoid cells and flat or concave mandibular condyles. Upper cervical spine instability along with compression of the spinal cord is a serious complication that can occur at any age in Morquio syndrome.