What Is Morquio Syndrome?

What Is Morquio Syndrome?

This rare disease, also called MPS IV, prevents the body from breaking down certain sugar molecules.

Morquio syndrome is a rare, inherited metabolic disorder that most often affects the skeleton.

Also known as MPS IV, Morquio syndrome is part of a group of diseases called mucopolysaccharidosis (MPS).

MPS is defined by the body’s inability to break down large sugar chains called glycosaminoglycans (formerly known as mucopolysaccharides).

As a result, these molecules build up in the body and interfere with cell function.

Prevalence

It’s unknown how many people are affected by MPS IV.

Some estimates place the rate at about 1 in 210,000 people, according to a case report.

The prevalence of the disorder also varies greatly by population.

For instance, it may occur in as many as 1 in 43,261 births among the Turkish population living in Germany, but in as few as 1 in 1,505,160 births in Sweden, according to an article.

Morquio affects males and females equally, and no ethnic group — broadly speaking — appears to have an increased risk for the disorder.

Types and Causes of Morquio Syndrome

There are two forms of Morquio syndrome, according to the Children’s Hospital of Philadelphia: Type A and Type B.

Morquio A syndrome, or MPS IVA, results from a deficiency in the enzyme galactosamine (N-acetyl)-6-sulfatase (GALNS).

Morquio B syndrome (MPS IVB), which is rarer and less severe than MPS IVA, results from a deficiency in the enzyme beta-galactosidase.

Without either of these enzymes, the body cannot break down certain glycosaminoglycans, particularly keratan sulfate.

Morquio syndrome is an autosomal recessive trait, according to MedlinePlus, meaning that you can only develop the disorder if you inherit two nonworking genes — one from your mother and one from your father.

Neither parent will likely show any signs or symptoms of the condition.

Symptoms and Complications

Glycosaminoglycans play an important role in building healthy bone, cartilage, corneas, skin, and connective tissue, including tendons and ligaments.

People with Morquio syndrome may experience issues with any of these body parts.

Symptoms, which usually begin between ages 1 and 3, may include:

  • Short stature with a short torso
  • Abnormal bone and spine development, including a curved spine (severe scoliosis)
  • Bell-shaped chest, with ribs that flare out at the bottom
  • Unusually flexible joints (hypermobile joints, also known as being double-jointed)
  • Knock-knees, or knees that angle inward and touch each other when the legs are straight
  • Teeth spaced widely apart
  • Abnormally large head (macrocephaly)
  • “Coarse” facial features, such as a bulging forehead
  • Cloudy vision
  • Heart valve issues and heart murmur
  • Enlarged liver

Over time, MPS IV may cause serious complications, including:

  • Spinal cord damage, which may result in paralysis
  • Blindness
  • Breathing problems and narrowed airways, which may cause frequent upper respiratory infections
  • Heart failure
  • Hearing impairment

Unlike some other types of MPS, Morquio syndrome doesn’t appear to cause intellectual disabilities.

Morquio Syndrome Diagnosis and Treatment

Diagnosis of Morquio syndrome typically begins with a physical examination, which can reveal various telltale signs of the disorder.

If you have signs or symptoms of MPS, your doctor will likely order a urine test to see if you have high levels of glycosaminoglycans.

Additional culture tests can detect unusual enzyme activity, and genetic tests (using saliva or blood) can reveal pathogenic variants indicative of MPS IV, according to MedlinePlus.

There is no cure for Morquio syndrome, and treatment is limited to supportive care of symptoms.

For example, physical therapy and surgical procedures, such as spinal fusion, may help with scoliosis and other bone and muscle issues.

In 2014, the Food and Drug Administration (FDA) approved the drug Vimizim (elosulfase alfa) for the treatment of MPS IVA.

Vimizim provides the body with the GALNS it’s missing, helping to improve physical endurance.

Morquio syndrome can significantly shorten a person’s lifespan due to spinal cord compression and breathing complications.

People with severe cases of MPS IV may only live into their twenties or thirties, and even people with mild cases don’t often live beyond age 60, according to one study.

Anna-Hurst-bio

Anna C.E. Hurst, MD, MS, FACMG

Medical Reviewer
Anna C. E. Hurst, MD, is a medical geneticist with board certification in clinical genetics and pediatrics. She is an associate professor in the department of genetics at University of Alabama at Birmingham (UAB) and an adjunct faculty member at the HudsonAlpha Institute for Biotechnology. Prior to medical school, she received a master’s degree in genetic counseling, which inspired her interest in the communication of genetic information to patients and families with rare diseases.

Dr. Hurst is a physician for the UAB Undiagnosed Disease program, Turner syndrome clinic, and general genetics clinic, and she provides hospital consultations for inpatients at UAB and Children’s of Alabama for general genetics and inborn errors of metabolism. She also is the medical geneticist for the Smith Family Clinic for Genomic Medicine in Huntsville, Alabama.

Hurst's research focuses on expanding the availability of genomic sequencing for children with complex healthcare needs. She also has an interest in how the patient’s physical exam and facial features can be clues to a rare disease diagnosis (dysmorphology) and serves on the scientific advisory board of Facial Dysmorphology Novel Analysis. She has published over 45 peer-reviewed articles in the field of medical genetics, largely focused on the clinical delineation of rare disease phenotypes. She also serves as an associate editor for the American Journal of Medical Genetics.

Hurst is also passionate about education and serves as the program director of the UAB genetics residency programs (categorical, pediatrics-genetics, and internal medicine-genetics) and medical director of the UAB Genetic Counseling Training program. She is an officer with the Association of Professors in Human Medical Genetics.

Joseph Bennington-Castro

Author

Joseph Bennington-Castro is a science writer based in Hawaii. He has written well over a thousand articles for the general public on a wide range topics, including health, astronomy, archaeology, renewable energy, biomaterials, conservation, history, animal behavior, artificial intelligence, and many others.

In addition to writing for Everyday Health, Bennington-Castro has also written for publications such as Scientific American, National Geographic online, USA Today, Materials Research Society, Wired UK, Men's Journal, Live Science, Space.com, NBC News Mach, NOAA Fisheries, io9.com, and Discover.

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