Definition

Morquio syndrome is an inherited disease of metabolism in which the body is missing or doesn't have enough of a substance needed to break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides).

The syndrome belongs to a group of diseases called mucopolysaccharidoses (MPS). Specifically, it is known as MPS IV.

See also:

• MPS I H (Hurler syndrome)
• MPS II, Hunter syndrome
• MPS III (Sanfilippo syndrome)
• MPS I S (Scheie syndrome)

Alternative Names

Mucopolysaccharidosis type IVA; Galactosamine-6-sulfatase deficiency; Mucopolysaccharidosis type IVB; Beta galactosidase deficiency; MPS IV

Causes, incidence, and risk factors

Morquio syndrome is an autosomal recessive trait. That means both your parents must pass you the defective gene in order for you to get this disease.

There are two forms of Morquio syndrome: Type A and Type B.

• Persons with Type A do not have a substance (enzyme) called galactosamine-6-sulfatase.
• Persons with Type B do not produce enough of an enzyme called beta-galactosidase.

The body needs these enzymes to break down a long strand of sugar molecules called the keratan sulfate sugar chain. In both types, abnormally large amounts of glycosaminoglycans build up in the body and brain, which can damage organs.

The syndrome is estimated to occur in 1 of every 200,000 births. Symptoms usually start between ages 1 and 3. A family history of the syndrome raises one's risk for the condition.

Symptoms

• Abnormal development of bones, including the spine
• Bell-shaped chest with ribs flared out at the bottom
• Coarse facial features
• Hypermobile joints
• Knock-knees
• Large head (macrocephaly)
• Short stature with a particularly short trunk
• Widely spaced teeth

Signs and tests

The doctor will perform a physical examination. Examination and testing may reveal:

• Abnormal curvature of the spine (kyphoscoliosis)
• Cloudy cornea
• Heart murmur (aortic regurgitation)
• Inguinal hernia
• Liver enlargement
• Loss of nerve function below the neck
• Short stature (especially short trunk)

Urine tests are usually done first. These tests may show extra mucopolysaccharides, but they can't determine the specific form of MPS.

Other tests may include:

• Blood culture
• Echocardiogram
• Genetic testing
• Hearing test
• Slit-lamp eye exam
• Skin fibroblast culture
• X-rays of the long bones, ribs, and spine

Persons with Morquio syndrome should have MRI of the lower skull and upper neck to determine if the upper vertebrae are underdeveloped.

Reviewer Info: Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the American Board of Genetic Counseling, University of Tennessee, Memphis, TN. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., 05/11/2009