Mucopolysaccharidosis (MPS)
Description
Mucopolysaccharidosis (MPS), also known as mucopolysaccharide storage disorders, is a group of genetic disorders that affect the body‘s ability to break down complex sugars called glycosaminoglycans (GAGs). These sugars are essential for the development and maintenance of various tissues, including cartilage, bones, and connective tissues. When MPS occurs, GAGs accumulate in cells and various organs, leading to a wide range of health problems.
Genes Involved
MPS is caused by mutations in various genes that encode enzymes involved in the breakdown of GAGs. The specific gene affected determines the type of MPS. Some of the genes involved include:
- IDUA (MPS I, Hurler Syndrome)
- IDS (MPS II, Hunter Syndrome)
- GNS (MPS III, Sanfilippo Syndrome)
- NAGLU (MPS IVA, Morquio Syndrome A)
- GALNS (MPS VI, Maroteaux-Lamy Syndrome)
- GLB1 (MPS VII, Sly Syndrome)
Recognizing the Signs and Symptoms
The signs and symptoms of MPS vary depending on the specific type of disorder and the severity. However, some common features include:
- Skeletal abnormalities: Short stature, joint stiffness, bone deformities, and spinal curvature
- Facial features: Coarse facial features, a large tongue, and a prominent forehead
- Cardiovascular problems: Heart valve defects, heart enlargement, and thickened heart walls
- Respiratory issues: Frequent respiratory infections, sleep apnea, and airway obstruction
- Neurological problems: Intellectual disability, seizures, and hearing loss
- Vision problems: Clouding of the cornea (cloudy eyes) and retinal degeneration
- Other: Enlarged liver and spleen, hernias, and skin problems
Causes
MPS is a genetic disorder, meaning it‘s caused by a mutation in a gene. These mutations are inherited from parents and can be passed down to children.
Inheritance/recurrence risk
Most types of MPS are inherited in an autosomal recessive pattern. This means that a person needs to inherit two copies of the mutated gene, one from each parent, to develop the disorder. If both parents carry one copy of the mutated gene, there is a 25% chance for each pregnancy that the child will inherit two copies and have MPS.
There is also a type of MPS, Hunter Syndrome (MPS II), which is inherited in an X-linked recessive pattern. This means that the gene responsible for the disorder is located on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. In X-linked recessive disorders, females need to inherit two copies of the mutated gene to develop the disorder, while males only need to inherit one copy.
