Mucopolysaccharidosis Type VI (MPS VI Maroteaux-Lamy syndrome)
Description
Mucopolysaccharidosis Type VI (MPS VI), also known as Maroteaux-Lamy syndrome, is a rare genetic disorder that affects the body‘s ability to break down complex sugar molecules called glycosaminoglycans (GAGs). These GAGs build up in various tissues, particularly in bones, cartilage, and the liver, leading to a range of symptoms.
Genes Involved
MPS VI is caused by mutations in the ARSB gene, which provides instructions for making an enzyme called arylsulfatase B. This enzyme breaks down a specific GAG called dermatan sulfate. When the ARSB gene is mutated, the enzyme is either missing or doesn‘t function properly, leading to the buildup of dermatan sulfate in the body.
Recognizing the Signs and Symptoms
The signs and symptoms of MPS VI can vary widely in severity and may include:
- Skeletal abnormalities: Short stature, disproportionate limbs, joint stiffness, spinal deformities (kyphosis, scoliosis), and hip dysplasia
- Facial features: Coarse facial features, prominent forehead, flat nasal bridge, and thick lips
- Cardiovascular problems: Heart valve abnormalities, cardiomyopathy (weakened heart muscle)
- Hepatosplenomegaly: Enlarged liver and spleen
- Hearing loss: Conductive hearing loss due to middle ear fluid buildup
- Corneal clouding: Opacity of the cornea, which can affect vision
- Dental problems: Delayed tooth eruption, enamel defects, and gum disease
- Neurological issues: In some cases, mild cognitive impairment or behavioral problems may occur.
Causes
MPS VI is an inherited disorder, meaning it is passed down through families. It is caused by a mutation in the ARSB gene, which is located on chromosome 5. The mutation can be inherited from one or both parents, or it can occur spontaneously.
Inheritance/recurrence risk
MPS VI is inherited in an autosomal recessive pattern. This means that an individual must inherit two copies of the mutated ARSB gene, one from each parent, to develop the disorder. If both parents carry one copy of the mutated gene, there is a 25% chance their child will inherit MPS VI. They also have a 50% chance of their child being a carrier, meaning they have one copy of the mutated gene but do not have the disorder themselves. There is a 25% chance their child will not inherit the mutated gene.
