Morquio syndrome is a rare metabolic condition that can cause a person to develop skeletal problems. The life expectancy of a person with Morquio syndrome can vary depending on the severity of their symptoms.

Symptoms of Morquio syndrome occur due to a gene alteration that a person inherits from their parents. These alterations allow the large sugar molecule keratan sulfate to build up to toxic levels inside a person’s cells.

The buildup of keratan sulfate can damage a person’s skeleton over time. It may also affect the eyes, heart, and respiratory system. A person with Morquio syndrome may have a reduction in life expectancy due to their condition.

In this article, we will discuss Morquio syndrome, including its symptoms, treatments, and outlook.

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Morquio syndrome, also known as MPS IV and mucopolysaccharidosis IV, is a rare metabolic condition. This term refers to a condition that disrupts a person’s metabolism.

Morquio syndrome is a form of mucopolysaccharidoses (MPS). These conditions affect the enzymes that the body uses to break down long chains of sugars, which play important roles, such as helping to build bone.

When a person has Morquio syndrome, they do not produce enough of certain enzymes that the body uses to break down keratan sulfate. This allows the keratan sulfate to build up to toxic levels, which can cause problems in a person’s:

  • bones
  • arteries
  • eyes
  • joints
  • ears
  • skin
  • teeth

Dr. Luis Morquio first discovered Morquio syndrome in Uruguay in 1929. That same year, Dr. James Brailsford also noted the symptoms of the condition in England. As such, the condition is sometimes known as Morquio-Brailsford syndrome.

Morquio syndrome is a rare condition, although its exact prevalence is unknown. Research estimates that it occurs in 1 in every 200,000 or 300,000 people. The National Organization of Rare Diseases (NORD) notes that the syndrome affects people of all genders equally.

The 1993 book Freak the Mighty by Rodman Philbrick includes a character who has Morquio syndrome.

There are two different subtypes of Morquio syndrome, known as MPS IVA and MPS IVB. Both subtypes can have the same symptoms. However, symptoms of MPS IVB are generally less severe than those of MPS IVA.

The subtype of Morquio syndrome a person has depends on what enzyme the condition relates to. MPS IVA occurs due to a lack of the enzyme N-acetyl-galactosamine-6-sulfatase (GALNS). MPS IVB occurs due to a deficiency in the enzyme beta-galactosidase.

NORD notes that 95% of people with Morquio syndrome have MPS IVA.

Morquio syndrome results from a variation in the genes responsible for creating enzymes. The enzyme a person is deficient in will depend on the subtype of Morquio syndrome they have.

MPS IVA occurs due to a variation in the GALNS gene, which affects the GALNS enzyme. MPS IVB occurs due to an alteration in the GLB1 gene, which impacts the beta-galactosidase enzyme.

A person has two copies of every gene in their body, one from each of their parents. Genes determine a person’s physical and behavioral traits. Morquio syndrome is an autosomal recessive condition. This means a person must receive a copy of the gene variation from both their parents to have the condition.

If both parents possess the gene alteration, their child will have a 25% chance of developing the condition.

Morquio syndrome can cause a person to develop various symptoms, which may vary in severity. Unlike some types of MPS, Morquio syndrome does not affect a person’s intelligence.

Symptoms of Morquio syndrome are progressive, meaning they develop over time. The first symptoms may appear during early childhood.

The symptoms include:

  • short stature
  • knock knees, where a person’s legs curve inwards, causing their feet to be apart when their knees touch
  • problems with the ribs, chest, spine, hips, wrists
  • loose, flexible joints
  • restricted movement in certain joints
  • underdevelopment of neck bones, resulting in a short neck
  • vision loss
  • recurrent ear infections
  • hearing loss
  • frequent upper respiratory tract infections
  • sleep apnea
  • excessive curvature of the spine known as kyphoscoliosis
  • flat feet
  • unusual development of the growing ends of the long bones
  • hip dislocation
  • arthritis
  • prominent breastbone
  • weakness of legs
  • facial characteristics such as a large head, broad mouth, prominent cheekbones, or small nose
  • widely spaced teeth with thin enamel
  • widely spaced eyes
  • enlarged liver or spleen
  • short torso
  • heart valve problems

A healthcare professional can diagnose a person with Morquio syndrome using:

  • a person’s medical history
  • physical examinations
  • skeletal X-rays
  • urine glycosaminoglycans (GAGs) analysis, which measures the amount of GAG in a person’s urine

Keratan sulfate is a type of GAG. If a person has high amounts of keratan sulfate in their urine, it can indicate that they have Morquio syndrome.

A healthcare professional can use genetic testing to check what subtype of Morquio syndrome a person has. Genetic testing involves taking a sample of a person’s tissue, such as blood or skin. A healthcare professional sends this sample to a laboratory, where technicians check for gene alterations.

There is currently no cure for Morquio syndrome. However, treatments are available to manage its symptoms.

Enzyme replacement therapy may help to slow the progress of MPS IVA. This treatment involves a person receiving enzymes via intravenous drip (IV) once a week. There is no enzyme replacement therapy available for MPS IVB.

A healthcare professional may offer the following treatments to manage a person’s symptoms:

  • surgery to fuse the bones of the upper neck to prevent potential damage to the spinal cord
  • surgery to correct respiratory or vision problems
  • physical rehabilitation
  • psychological support
  • learning optimization for people with difficulty seeing or hearing
  • mobility aids
  • genetic counseling to help a person understand their diagnosis and treatment options

The outlook for a person with Morquio syndrome can depend on the severity of their symptoms.

Evidence suggests that people with severe symptoms may only live until late childhood or adolescence. People with milder symptoms generally live into adulthood. However, their life expectancy may be lower.

If a person has a poorly developed connection between their first and second vertebrae due to Morquio syndrome, it can be life threatening. Minor injuries may cause the two vertebrae to slip, which can compress the spinal cord. Surgery is available that can fuse the two vertebrae, but life expectancy will still be lower.

Problems with a person’s chest due to Morquio syndrome can put a strain on their heart and lungs. This may lead to respiratory failure.

Evidence notes that spinal cord compression and airway obstruction are the two main causes of death for a person with Morquio syndrome.

Morquio syndrome is a rare metabolic condition. It causes a person to develop skeletal problems due to a buildup of a sugar known as keratan sulfate.

There are two subtypes of the syndrome. Each subtype affects a different gene, causing a lack of either the GALNS or beta-galactosidase enzymes.

Currently, there is no cure for Morquio syndrome. However, there are treatments available to manage its symptoms. The outlook for a person depends on the severity of their symptoms. Having this condition may reduce a person’s life expectancy.