Morquio's syndrome

Morquio syndrome (referred to as mucopolysaccharidosis IV or Morquio) is a mucopolysaccharide storage disease (see also lysosomal storage disorder), usually inherited. Morquio is a relatively rare metabolic disorder in which the body cannot process certain types or mucopolysaccharides. When the body cannot process certain types of mucopolysaccharides, they build up or are eliminated, causing various symptoms. It is usually an inherited disease.

The disease is caused by an abnormal accumulation of mucopolysaccharides – in this case, keratan sulfate – in the body. Keratan sulfate is excreted in urine.

The symptoms vary from patient to patient, and may include hearing loss, cataracts, skeletal dysplasia, spinal instability, and minor respiratory issues, among others.

Two forms are recognized, type A and type B.

• Morquio type A is a deficiency of the enzyme N-acetylgalactosamine-6-sulfate sulfatase.
• Morquio type B is the deficiency of the enzyme beta-galactosidase.

The condition was first described, simultaneously and independently, in 1929, by Luis Morquio in Montevideo, Uruguay, and by James Frederick Brailsford in Birmingham, England. They both recognized the occurrence of corneal clouding, aortic valve disease, and urinary excretion of keratan sulfate. Morquio observed the disorder in 4 siblings in a family of Swedish extraction and reported his observations in French.

The following symptoms are associated with Morquio syndrome:

• Abnormal heart development
• Abnormal skeletal development
• Hypermobile joints
• Large fingers
• Knock-knees
• Widely spaced teeth
• Coarse facial features
• Large head
• Star shaped chest (ribs flared)
• Compression of spinal cord

As most mucopolysaccharidoses, Morquio syndrome exhibits alterations in white blood cells that are diagnostic, and might allow for screening procedures and cost-effective differential diagnosis in the future. These anomalies can be best studied with Wright stain, the routine dye employed in hematology laboratory. Neutrophils in Morquio’s syndrome exhibit persistence of the azurophilia in its granules, which is explained by the deficient enzyme’s inability to clear them from mucopolysaccharides used as a tags in the cells vesicular sorting system. Approximately 70 percent of the neutrophils exhibit this subtle alteration. Differential diagnosis must be made with mucopolisaccharidoses I,II,III,VI and VII.

Nonetheless, after this screening procedure has been carried on, quantitative enzyme determination assays must be conducted to verify the diagnosis, should any replacement treatment is available.

Complications that may develop include:

• 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
• Problems with urination

• Radiographic features include oval-shaped vertebral bodies with anterior beaking, unossified femoral heads with proximal femoral valgus deformities, and broad, flat ilia.
• By 2 to 3 years of age, universal platyspondyly with central beaking is almost pathognomonic.
• The long tubular bones are thickened and shortened as well.

• National MPS Society
• www.morquio.com

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