Morquio Syndrome (Mucopolysaccharidosis IV)
What is Morquio Syndrome (Mucopolysaccharidosis IV)?
Morquio Syndrome, also known as Mucopolysaccharidosis IV (MPS IV), is a rare genetic disorder that affects the body’s skeletal development. Individuals with MPS lack the ability to break down complex carbohydrates known as glycosaminoglycans (GAGs). These were originally known as mucopolysaccharides, which is how this disease came to be known as MPS. The high amount of GAGs in the body accumulate in the lysosomes of cells, and are at highest levels in bone cells which affects the skeleton. There are two types of Morquio Syndrome. Type A is characterized by a deficiency of the enzyme N-acetylgalactosamine-6-sulfatase, and Type B is characterized by a deficiency of the enzyme beta-galactosidase. The enzyme deficiencies lead to an accumulation of GAGs in tissues and organs, causing a range of clinical symptoms and many skeletal abnormalities.
Synonyms
Morquio Syndrome, also known as Mucopolysaccharidosis IV (MPS IV), is a rare genetic disorder that affects the body’s skeletal development. Individuals with MPS lack the ability to break down complex carbohydrates known as glycosaminoglycans (GAGs). These were originally known as mucopolysaccharides, which is how this disease came to be known as MPS. The high amount of GAGs in the body accumulate in the lysosomes of cells, and are at highest levels in bone cells which affects the skeleton. There are two types of Morquio Syndrome. Type A is characterized by a deficiency of the enzyme N-acetylgalactosamine-6-sulfatase, and Type B is characterized by a deficiency of the enzyme beta-galactosidase. The enzyme deficiencies lead to an accumulation of GAGs in tissues and organs, causing a range of clinical symptoms and many skeletal abnormalities.
Morquio Syndrome has an estimated prevalence of 1 in 200,000 to 1 in 300,000 live births.
| Name | Abbreviation |
|---|---|
| MPS IV Mucopolysaccharidosis Type IV Morquio A Syndrome (for the N-acetylgalactosamine-6-sulfatase deficiency) Morquio B Syndrome (for the beta-galactosidase deficiency) Morquio-Brailsford syndrome | |
| MPS IV Mucopolysaccharidosis Type IV, Morquio A Syndrome (for the N-acetylgalactosamine-6-sulfatase deficiency), Morquio B Syndrome (for the beta-galactosidase deficiency), Morquio-Brailsford syndrome |
Morquio Syndrome is caused by mutations in the genes responsible for the breakdown of GAGs. Type A is associated with the GALNS gene which produces the enzyme N-acetylgalactosamine-6-sulfatase, and Type B is associated with the GLB1 gene which produces the enzyme beta-galactosidase. The two types of MPS IV cannot be distinguished by symptoms alone, and must be diagnosed with genetic testing for abnormalities in one of the two possible genes. The disease is inherited in an autosomal recessive pattern, where both parents must be carriers of the genetic mutation to have an affected child. Carriers are asymptomatic. There is a 25% chance of having an affected child if both parents are carriers (see RareShare Guide on Genetic Inheritance).
The Type A enzyme deficiency leads to an accumulation of the GAGs keratan sulfate and chonroitin-6-sulfate in various tissues; the Type B deficiency causes an accumulation of keratan sulfate only. This can be used to diagnose an individual with either Type A or Type B via a blood test.
Symptoms of Morquio Syndrome typically appear in early childhood and can include:
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Skeletal abnormalities: Short stature, abnormal growth of bones, joint laxity and scoliosis (sideways curvature of the spine).
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Facial features: Coarse facial features, prominent forehead and a broad mouth.
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Dental issues: Widely spaced teeth, enamel defects.
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Cardiovascular complications: Heart valve disease.
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Respiratory issues: Frequent respiratory infections, airway obstruction.
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Hearing and vision problems: Hearing loss, corneal clouding.
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Other: Hepatosplenomegaly (enlarged liver and spleen), hernias and reduced endurance.
While both types share many clinical symptoms, such as skeletal abnormalities, short stature and joint issues, the severity and specific manifestations are variable. Generally, Type A may have more pronounced symptoms compared to Type B. A diagnosis can confirm the type of MPS IV.
Diagnosis of Morquio Syndrome typically involves:
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Clinical evaluation: Assessment of symptoms and physical examination.
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Radiological imaging: X-rays and MRIs to identify skeletal abnormalities.
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Biochemical tests: Measurement of GAG levels in urine.
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Enzyme assay: Identification of deficient enzyme activity in blood or fibroblasts.
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Genetic testing: Identification of mutations in the genes GALNS (for Type A) or GLB1 (for Type B).
Specialized tests: Echocardiograms for heart function, hearing and vision tests.
There is no cure for Morquio Syndrome. Treatment generally focuses on managing symptoms and improving quality of life. This includes:
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Enzyme Replacement Therapy (ERT): For Morquio A, ERT with elosulfase alfa (Vimizim) can help reduce the accumulation of GAGs.
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Surgical interventions: To correct skeletal abnormalities, improve airway function, and address other complications.
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Supportive care: Physical therapy, respiratory therapy, and management of cardiovascular issues.
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Regular monitoring: For complications and disease progression.
Hematopoietic Stem Cell Transplantation (HSCT): Used in some cases to provide a long-term enzyme source.
The prognosis for individuals with Morquio Syndrome can vary widely depending on the severity of symptoms and the type of the disorder. Early diagnosis and comprehensive management can significantly improve the quality of life and lifespan. Individuals with Type A generally have a poorer prognosis due to severity of symptoms and complications. Lifespan is often reduced, with many patients living into their 20s and 30s. The prognosis for patients with Type B can be better due to milder symptoms. Some patients may have a normal lifespan, although the quality of life can still be affected by skeletal or other systemic issues.
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National MPS Society: MPS IV.
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Hendriksz CJ, et al. (2013). Mucopolysaccharidosis type IVA (Morquio A syndrome): a review of clinical presentation, diagnosis, and treatment. Mol Genet Metab. MPS IV Review.
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https://medlineplus.gov/genetics/condition/mucopolysaccharidosis-type-iv/
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Enrolling is easy.
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After these steps, the enrollment process is complete. All other questions are voluntary. However, these questions are important to patients and their families to create awareness as well as to researchers to study rare diseases. This is why we ask our participants to update their information annually or anytime changes to their information occur.
Researchers can contact CoRDS to determine if the registry contains participants with the rare disease they are researching. If the researcher determines there is a sufficient number of participants or data on the rare disease of interest within the registry, the researcher can apply for access. Upon approval from the CoRDS Scientific Advisory Board, CoRDS staff will reach out to participants on behalf of the researcher. It is then up to the participant to determine if they would like to join the study.
Visit sanfordresearch.org/CoRDS to enroll.
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