Mucopolysaccharidosis type IVA or Morquio syndrome A is a lysosomal storage disorder characterized by skeletal dysplasia due to excessive storage of keratan sulfate. Affected individuals usually present with unusual skeletal features including short trunk dwarfism, odontoid hypoplasia, pectus carinatum, kyphosis, gibbus, scoliosis, genu valgus, coxa valga, and flaring of the lower ribs. Hypermobile joints and an abnormal gait with a tendency to fall may also be presenting features. Unlike other mucopolysaccharidoses (MPS) intelligence is often preserved. Odontoid hypoplasia is the most serious skeletal finding because, in combination with ligamentous laxity and mucopolysaccharide deposition, it may result in atlantoaxial subluxation, cervical myelopathy or even death. Other possible features include pulmonary compromise, valvular heart disease, hearing loss, hepatomegaly, fine corneal clouding, and widely spaced teeth with abnormally thin enamel with increased risk of caries formation. Patients may also have coarse facial features, although this is usually milder than that seen in MPSI or MPSII. Patients appear healthy at birth with initial symptoms usually presenting by the age of 3 years, at which time the patient is usually evaluated due to the unusual skeletal features. Morquio syndrome A patients exhibit a wide spectrum of clinical symptoms and more mildly affected patients may have a normal quality of life and mild bone and visceral organ involvement. The incidence of Morquio syndrome A has been estimated to be from 1 in 76,000 in Northern Ireland to 1 in 450,000 in Portugal.