Beta galactosidase deficiency

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

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

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

Exams 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.

Treatment

There is no specific treatment for Morquio syndrome. Symptoms are treated as they occur.

A spinal fusion may prevent irreversible spinal cord injury in persons whose neck bones are underdeveloped.

Support Groups

National MPS Society --www.mpssociety.org

Outlook (Prognosis)

Cognitive function is usually normal in patients with Morquio syndrome.

Bone problems can lead to significant complications. For example, the small bones at the top of the neck may slip and damage the spinal cord, causing paralysis. Surgery to correct such problems should be done if possible.

Cardiac complications may lead to death.

Possible Complications

• Breathing problems
• Heart failure
• Spinal cord damage and possible paralysis
• Vision problems
• Walking problems related to abnormal curvature of the spine and other bone problems

When to Contact a Medical Professional

Call your health care provider if symptoms of Morquio syndrome occur.

Prevention

Genetic counseling is recommended for prospective parents with a family history of Morquio syndrome.

National Institute of Neurological Disorders and Stroke. Mucolipidoses Fact Sheet. Office of Communications and Public Liaison. Bethesda, MD; Publication No. 03-5115. February 13, 2007.