Morquio syndrome is an inherited disease belonging to the group of mucopolysaccharide storage diseases. Two forms are recognized and called either A or B. Type A disease is characterized by the absence of the enzyme galactosamine-6-sulfatase, and the excretion of keratan sulfate in the urine. Type B disease results from deficiency of beta galactosidase enzyme. In both types there is accumulation in the body and brain of abnormally large amounts of a substance called mucopolysaccharide.
Alternative Names
Mucopolysaccharidosis type IVA = galactosamine-6-sulfatase deficiency; Mucopolysaccharidosis type IVB = beta galactosidase deficiency
Causes, incidence, and risk factors
Morquio syndrome is transmitted as an autosomal recessive trait. It has several symptoms in common with other mucopolysaccharide storage diseases such as coarse facial features, short stature , and skeletal and joint abnormalities. Like Sanfilippo syndrome , onset of symptoms is delayed until after the first year, and life expectancy may exceed 20 years. Unlike Sanfilippo syndrome, the mental development is often normal.
Signs and tests
Physical examination and testing shows:
Cloudy corneaHepatomegaly ( liver enlargement )
Inguinal hernias Kyphoscoliosis (abnormal curvature of the spine) Short stature (especially short trunk) Aortic regurgitation (heart murmur) Loss of nerve function below the neck Tests
X-ray of the long bones
X-ray of the ribsX-ray of the spine shows abnormal vertebrae and osteoporosis Urine chemistry , keratosulfate or chondroitin sulfate may be increased Culture of skin fibroblasts or white blood cells for deficient galactosamine-6-sulfatase or beta galactosidase enzyme activity
Hearing testSlit-lamp eye exam for abnormal deposits in cornea Echocardiogram may show thickened heart valves Genetic testing may be available
Treatment
There is no specific treatment for Morquio syndrome. Symptoms are treated as they occur. Patients with Morquio syndrome should have MRI of the lower skull and upper neck to determine if the upper vertebrae are underdeveloped. If they are a spinal fusion may prevent irreversible spinal cord injury. Bone marrow transplantation or enzyme replacement therapy may be available in the future.
Support groups
National MPS Society, Inc. 610-942-0100, www.mpssociety.org
Expectations (prognosis)
Bony abnormalities represent a significant problem, and correction through surgery should be made where possible. For example, small vertebrae at the top of the neck can cause slippage that damages the spinal cord so that paralysis may result. Death may occur as a result of cardiac complications.
Prevention
Genetic counseling is recommended for prospective parents with a family history of Morquio syndrome.