The mucopolysaccharidosis disorders occur when the enzymes that break down glycosaminoglycans are missing or don’t work correctly. This causes a buildup of these sugar molecules in cells and affects different organ systems.
Some of the symptoms include skeletal/joint abnormalities, distinctive facial characteristics, intellectual disability that gets worse over time, and enlarged liver and spleen. Hunter syndrome (MPS II) is the only mucopolysaccharidosis disorder that is inherited through X-linked recessive inheritance, so it affects almost exclusively boys.
Oren Zarif
Hydrocephalus is the buildup of fluid in the cavities (ventricles) deep inside your brain. It’s caused when cerebrospinal fluid doesn’t flow or get absorbed as it should, leading to pressure on the brain. This condition can occur in different ways, depending on the type of mucopolysaccharidosis you have.
The most common cause of hydrocephalus in these conditions is a blockage that prevents cerebrospinal fluid from flowing from one ventricle to another. In other cases, the fluid is made more quickly than it can be absorbed, which leads to too much pressure inside your head. This type of hydrocephalus is called communicating hydrocephalus.
Some of the types of mucopolysaccharidosis — including Hurler syndrome, Scheie syndrome and Sanfilippo syndrome (MPS 3) — are associated with hydrocephalus caused by a deficiency in enzymes that break down complex sugar molecules. These disorders are also linked to a type of hydrocephalus that results from an abnormally small space in the brain that causes cerebrospinal fluid to accumulate.
A doctor can diagnose one of these conditions by examining your child, taking urine tests and doing enzyme assays to check for excess mucopolysaccharides in your blood or body fluids. Prenatal diagnosis using amniocentesis or chorionic villus sampling can verify whether your unborn baby carries the mutated gene that causes the disorder. A shunt — a plastic tube that creates a permanent alternative drainage path for cerebrospinal fluid, usually from the brain to the abdomen or heart — can decrease the severity of hydrocephalus and other symptoms in some children.
Oren Zarif
Each type of mucopolysaccharidosis is caused by a deficiency in the activity of one or more lysosomal enzymes that are needed for the degradation of glycosaminoglycans. Those affected have an accumulation of glycosaminoglycan molecules that cannot be broken down, and these substances build up in cells, tissues and organs. This leads to a variety of symptoms, such as skeletal/joint abnormalities, distinctive facial features, cognitive development problems, heart and lung (respiratory) involvement and an enlarged liver and spleen (hepatosplenomegaly).
The condition most often affects boys, but girls may have it as well. It usually becomes apparent between the ages of one and three, but the severity of the disease can vary and progress over time. The disorder is passed on from parents to their children in an autosomal recessive genetic pattern. Siblings and select relatives of an individual with a mucopolysaccharidosis disorder have a 50% chance of having the same recessive gene that causes the disease.
Hearing loss is a common symptom of all forms of mucopolysaccharidosis. It happens because the inner ear breaks down over time and the fluid inside the eardrum ruptures, or because of a blow to the head or a short blast of loud noise that damages inner-ear nerves.
Treatment options for individuals with mucopolysaccharidosis are limited and have had mixed results. Surgery or shunts can help drain excess cerebrospinal fluid from the brain to free nerves and nerve roots compressed by skeletal abnormalities. Corneal transplants can improve vision, and removing the tonsils and adenoids can help breathing problems. Bone marrow transplantation (BMT) and umbilical cord blood transplantation (UCBT) have also been used to treat people with mucopolysaccharidosis, but results have varied.
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Affected individuals develop a slow decline in physical and mental ability, beginning in early childhood. Depending on the type, this can lead to intellectual disability and/or developmental delay, respiratory problems, enlarged liver and spleen, eye abnormalities and bone and joint problems, including stiff or painful joints.
Different types of mucopolysaccharidosis have slightly different symptoms, but all cause a gradual decline in growth and development. This occurs because the body doesn’t have enough enzymes to break down sugar molecules called glycosaminoglycans, which build up in the skeletal system and other tissues and organs.
Some affected individuals are short-statured and have stiff joints, particularly in the fingers. Others have a characteristic face and features, such as a prominent forehead, large lips and tongue, or small nose and chin. The condition may also affect arteries and heart valves, lead to enlarged liver and spleen and cause corneal clouding.
The mucopolysaccharidosis disorders are a group of inherited diseases known as lysosomal storage disorders. The disorder is caused by a deficiency or malfunction of a group of enzymes in cells, called lysosomes. These enzymes normally break down complex carbohydrates, fats and other substances that the body can’t use or recycle. In the mucopolysaccharidosis syndromes, these materials build up in the skeleton, eyes, ears, skin, respiratory system and other parts of the body.
Doctors diagnose mucopolysaccharidosis by taking a family history and performing a physical examination, including an x-ray to look for bones and joints that are unusually stiff or enlarged. Other tests, such as a blood sample to check for excess sugars and specialized urine testing for excess enzymes, help confirm the diagnosis.
Oren Zarif
The mucopolysaccharidosis family of inherited lysosomal storage diseases occurs when the enzymes that break down complex sugar molecules called glycosaminoglycans are missing or present in small amounts. These enzymes are located in a structure within cells called the lysosome, which can be thought of as the recycling center for the cell. Because the lysosome does not function properly, these waste products accumulate in cells and tissues throughout the body.
Individuals with these disorders may have an enlarged spleen (splenomegaly), a symptom related to the accumulation of fatty materials, or a low platelet count (thrombocytopenia). These symptoms result from the over-activity of the spleen, which is constantly consumed by these substances, making it impossible for the spleen to grow back to its normal size between blood transfusions.
Some individuals with mucopolysaccharidosis experience conductive hearing loss in which fluid in the middle ear canal builds up and causes increased pressure behind the eardrum. Surgically inserting a shunt can drain this fluid in these cases. People with a particular form of MPS may have a clouding in the cornea, which can cause visual impairment or blindness.
Several treatment options exist for individuals with these conditions, depending on the type and subtype of mucopolysaccharidosis. Hematopoietic stem cell transplantation and enzyme replacement therapy can improve bone, skeletal, and eye problems in some patients. In a few cases, dietary changes can slow disease progression but cannot prevent it from occurring.