Mucopolysaccharidosis type IVB (beta galactosidase deficiency)

Alternative names 
Mucopolysaccharidosis type IVA (galactosamine-6-sulfatase deficiency); Morquio syndrome

Definition

Morquio syndrome is an inherited disease belonging to the group of Mucopolysaccharide storage diseases. Two forms are recognized, type A and type 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 the enzyme beta galactosidase.
In both types there is accumulation in the body and brain of abnormally large amounts of a substance called Mucopolysaccharide.

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.

Symptoms

     
  • Family history of Morquio syndrome  
  • Coarse facial features (more mild than either Hunter syndrome or Hurler syndrome)  
  • 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 many bones including the spine  
  • Compression of the spinal cord can lead to weakness or paralysis

Signs and tests

Physical examination and testing shows:

     
  • Cloudy cornea  
  • 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 ribs  
  • X-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 test  
  • Slit-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
http://www.mpssociety.org

Expectations (prognosis)
Bone 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.

Complications

     
  • Heart failure  
  • Difficulty with vision  
  • Walking problems related to abnormal curvature of the spine  
  • Abnormal neck bones can cause spinal cord damage that can cause severe disease including paralysis if not caught early; spinal fusion can prevent this  
  • Breathing problems

Calling your health care provider
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.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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