Mucopolysaccharidosis Type IV (MPS IV Morquio syndrome)

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Description

Morquio syndrome, also known as mucopolysaccharidosis type IV (MPS IV), is a rare genetic disorder that primarily affects the skeletal system. Individuals with Morquio syndrome experience progressive skeletal deformities due to the buildup of specific complex sugars, known as glycosaminoglycans (GAGs), in the body. This buildup disrupts normal cartilage development and bone growth, leading to a range of physical challenges. This blog provides a comprehensive overview of Morquio syndrome, covering its causes, symptoms, diagnosis, management, and resources for support.

Genes Involved

Genes Involved in Morquio Syndrome:

• MPS IVA: Caused by mutations in the GALNS gene, responsible for the enzyme N-acetylgalactosamine-6-sulfatase. This enzyme breaks down keratan sulfate, a type of GAG.
• MPS IVB: Caused by mutations in the GLB1 gene, responsible for the enzyme beta-galactosidase. This enzyme breaks down galactosylceramide, a lipid involved in myelin formation.

Recognizing the Signs and Symptoms

Recognizing the Signs and Symptoms of Morquio Syndrome:

• Skeletal Deformities:
  • Short stature (dwarfism)
  • Enlarged head (macrocephaly)
  • Spinal curvature (kyphosis, scoliosis)
  • Joint stiffness and pain
  • Knock-knees or bowlegs
  • Barrel-shaped chest
• Cardiovascular Issues:
  • Heart valve problems
  • Aortic valve stenosis
  • Enlarged heart (cardiomegaly)
• Respiratory Difficulties:
  • Narrowed airways
  • Frequent respiratory infections
  • Sleep apnea
• Vision Problems:
  • Corneal clouding
  • Cataracts
• Hearing Loss:
  • Conductive hearing loss
• Other Symptoms:
  • Delayed development
  • Intellectual disability (in some cases)
  • Liver and spleen enlargement (hepatosplenomegaly)
  • Hernias

Causes

Causes of Morquio Syndrome:

Morquio syndrome is an inherited disorder, meaning it is passed down from parents to their children. It occurs due to mutations in specific genes responsible for producing enzymes necessary for breaking down complex sugars called glycosaminoglycans (GAGs). These GAGs accumulate in various tissues, primarily affecting cartilage and bone development.

Inheritance/recurrence risk

Inheritance and Recurrence Risk:

Morquio syndrome is inherited in an autosomal recessive pattern. This means that both parents must carry a copy of the mutated gene for their child to inherit the disorder. If both parents are carriers, there is a 25% chance with each pregnancy that their child will inherit Morquio syndrome. There is also a 50% chance their child will be a carrier of the mutated gene, and a 25% chance their child will not inherit the mutated gene.