Morquio Syndrome (MPS IVA)

Background and History: 

Lu??s Morquio, a pediatrician from Uruguay, and James Frederick Brailsford, a British radiologist, independently first described children with this disorder in 1929.   Morquio syndrome belongs to a group of disorders called mucopolysaccharidoses, so-called because mucopolysaccharides, composed of long chains of sugar molecules, accumulate in cells throughout the body as the result of an enzyme deficiency.

Clinical Correlations: 

Morquio syndrome is actually two disorders, types A and B, caused by two different enzyme defects.  Type A is the more severe but there is considerable variation in the clinical symptoms.  Newborns are generally normal but since this is a progressive disease, symptoms develop gradually.  Most children are diagnosed by the age of 6 years.  Unlike other mucopolysaccharidoses, there is no primary neurologic damage and no mental deficiency.  Bone development is abnormal resulting in a short neck, and truncal dwarfism.  Joints, especially the knees and hips, may be deformed sometimes causing mobility problems.  The vertebrae are malformed leading to deformity of the spine and sometimes breathing problems.  The most serious defect is at the base of the skull with underdevelopment of a specific bone called the odontoid process which results in instability of the skull-spinal column alignment and if dislocated can damage the spinal cord with serious consequences in bladder and intestinal function.  The upper teeth are abnormally wide and have increased space between them.  Some patients have abnormal heart rhythms and others have hearing problems.

The cornea (windshield) of the eye is cloudy as the result of a myriad of fine opacities which accumulate in it.  These may not appear until late in the first decade of life.  Vision is impacted to some extent but corneal transplantation is rarely required.  Rare patients have glaucoma.


This is an autosomal recessive disorder caused by a mutation in a gene that codes for an enzyme needed for mucopolysaccharide metabolism.  Parents are usually clinically normal but are carriers of a single mutation.  Their second normal copy compensates and metabolism is normal.  Children who inherit a mutation from each parent are affected with Morquio syndrome because they have two defective copies and no normal one to compensate for the enzyme defect.

Diagnosis and Prognosis: 

A pediatrician is most likely to make the diagnosis.   The urine contains abnormal metabolic products which are often diagnostic.  X-rays of joints may also be used to confirm the diagnosis.  Ophthalmologists are needed to confirm the corneal deposits but these may not appear until several years of age.  Orthopedists may suggest surgery for joint deformities and sometimes to stabilize the spine.  The prognosis is highly variable depending on the severity of disease but patients can live into adulthood.  Some individuals have lived into the seventh decade of life.

Additional Information
Autosomal recessive