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Mucopolysaccharidoses (MPS) and mucolipidosis (ML) are genetic lysosomal storage diseases (LSD) caused by the body’s inability to produce specific enzymes. The missing or insufficient enzyme prevents cells from recycling waste, resulting in the storage of materials in cells throughout the body. As the disease progresses, there is widespread damage throughout the body, including the heart, bones, joints, respiratory system and central nervous system, leading to a shortened lifespan.
The National MPS Society provides support to families and promotes research initiatives that affect the following diseases:
In a continuing effort to provide support and information to individuals about MPS and ML, the National MPS Society has created a central location for more information on MPS.
MPS I is a mucopolysaccharide disease also called Hurler, Hurler-Scheie and Scheie syndrome. Hurler takes its name from Gertrude Hurler, the doctor who described a boy and girl with the condition in 1919. In 1962, Dr. Scheie, a consultant ophthalmologist, wrote about patients who were more mildly affected. Individuals who do not fit the severe or mild ends of the disease were said to have Hurler/Scheie. The specific disease names have been replaced with the designations attenuated (diminished severity) and severe MPS I. MPS I has a wide range of symptoms that vary in severity and can be managed and treated with enzyme replacement therapies. There is no cure for MPS I.
Mucopolysaccharides are chains of sugar molecules used to build connective tissues in the body.
The body constantly replaces used materials and breaks them down for disposal. MPS I patients are missing the enzyme alpha-L-iduronidase, which is essential in breaking down the mucopolysaccharides dermatan sulfate and heparan sulfate. These materials remain stored in the body’s cells, causing progressive damage. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
MPS I (Hurler-Scheie) is a continuum of severity based upon the symptoms, ranging from severe to attenuated. There is a great deal of variability of symptoms among individuals with MPS I, often making the specific designation difficult. Generally, severe MPS I will present within the first year of life while less severe (attenuated) forms present during childhood. Although individuals with attenuated MPS I have normal intelligence, they may have a variety of symptoms that can range from mild to severe.
Severe MPS I occurs in approximately 1 in 100,000 newborns. Attenuated MPS I is less common and occurs in about 1 in 500,000 newborns.
MPS I (Hurler-Scheie syndrome ) is caused by a recessive gene. There is a one in four chance with every pregnancy that the child will inherit the defective gene from each carrier parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of children with MPS I will be carriers.
There is no cure but treatments such as bone marrow transplantation and/or enzyme replacement therapy (ERT) can help make MPS I a more manageable disease. Aldurazyme is the first and only FDA approved ERT treatment developed through recombinant DNA technology for individuals with MPS I.
MPS II is a mucopolysaccharide disease known as Hunter syndrome. It takes its name from Charles Hunter, the professor of medicine in Manitoba, Canada, who first described two brothers with the disease in 1917. MPS II has a wide range of symptoms that vary in severity and can be managed and treated with enzyme replacement therapies. There is no cure for MPS II.
Mucopolysaccharides are chains of sugar molecules used to build connective tissues in the body.
The body constantly replaces used materials and breaks them down for disposal. MPS II patients are missing the enzyme iduronate sulfatase, which is essential to breaking down the mucopolysaccharides dermatan and heparan sulphate. These materials remain stored in the body’s cells, causing progressive damage. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
This is a rare condition affecting 1 in 100,000 to 1 in 170,000 primarily males.
MPS II primarily occurs in boys, and girls may be carriers of the gene for MPS II. Although rare, MPS II has been diagnosed in girls. If the mother is a carrier, there is a 50 percent chance that any boy born will have the disease. The sisters and maternal aunts of a person with MPS II may be carriers of the disease and would also have a 50 percent chance of passing the syndrome to a son.
There is no cure, but treatments like enzyme replacement therapies can help make the disease more manageable.
MPS III is a mucopolysaccharide disease also known as Sanfilippo syndrome. It takes its name from Dr. Sylvester Sanfilippo, one of the U.S. doctors who described the condition in 1963.
Mucopolysaccharides are chains of sugar molecules used to build connective tissues in the body.
The body constantly replaces used materials and breaks them down for disposal. MPS III patients are missing an enzyme essential to breaking down the mucopolysaccharide heparan sulphate. These materials remain stored in the body’s cells, causing progressive damage. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
To date, four different enzyme deficiencies have been found to cause MPS III, described as type A, B, C or D.
There is usually little difference between the four types, but some mild cases of the B form saw affected individuals stay relatively healthy into adult life.
MPS III is the most common form of mucopolysaccharidosis, and 1 in 70,000 newborns are born with the disease. MPS III A and MPS III B are more common than MPS III C and MPS III D.
MPS III is caused by a recessive gene. There is a one in four chance with every pregnancy that the child will inherit the defective gene from each carrier parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of MPS III patients will be carriers.
There is no cure for MPS III and no current approved treatment. Enzyme replacement therapy (ERT) has not been shown to be effective in MPS III. Bone marrow transplants have been tried on individuals with MPS III, but with disappointing results. Gene therapy, chaperone therapy and intrathecal enzyme therapy are a few of the treatments for MPS III where research is ongoing.
The disease affects each person differently, and its progress will be much faster in some individuals than in others. Symptoms often appear after age 1, and learning abilities begin to slow between ages 2 and 6. Normal growth continues during the first few years, but will begin to slow, and final height is below average. Delayed development is followed by worsening mental status.
Other symptoms include:
MPS IV is a mucopolysaccharide disease known as Morquio or Morquio-Brailsford syndrome. MPS IV takes its name from Dr. Morquio, a pediatrician in Montevideo, Uruguay, who in 1929 described a family of four children affected by this condition. As the same condition was also described in the same year by Dr. Brailsford from Birmingham, England, it is sometimes known as Morquio-Brailsford syndrome. MPS IV has a wide range of symptoms that vary in severity and can be managed and treated with enzyme replacement therapies. There is no cure for MPS IV.
Mucopolysaccharides are chains of sugar molecules used to build connective tissues in the body.
The body constantly replaces used materials and breaks them down for disposal. MPS IV patients are missing an enzyme essential to breaking down the mucopolysaccharide keratan sulfate. These materials remain stored in the body’s cells, causing progressive damage. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
MPS IV is one of the rarest of the MPS diseases in the United States. Reliable incidence figures are not available, but estimates find the disease in 1 in 200,000 to 300,000 individuals.
MPS IV is caused by a recessive gene. There is a one in four chance with every pregnancy that the child will inherit the defective gene from each carrier parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of children with MPS IV will be carriers.
There is no cure for MPS IV. In 2014, Vimizin was approved by the FDA as a enzyme replacement therapy for MPS IVA. There is no treatment for MPS IVB.
MPS IV is a mucopolysaccharide disease known as Maroteaux-Lamy Syndrome. It takes its name from two French Doctors, Dr. Maroteaux and Dr. Lamy, who first described the condition in 1963. MPS VI has a wide range of symptoms that vary in severity and can be managed and treated with enzyme replacement therapies. There is no cure for MPS VI.
Mucopolysaccharides are chains of sugar molecules used to build connective tissues in the body.
The body constantly replaces used materials and breaks them down for disposal. MPS VI patients are missing an enzyme essential to breaking down the mucopolysaccharide dermatan sulfate. These materials remain stored in the body’s cells, causing progressive damage. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
MPS VI is estimated to occur in 1 in 250,000 to 600,000 newborns.
MPS VI (Maroteaux-Lamy syndrome) is caused by a recessive gene. There is a one in four chance with every pregnancy that the child will inherit the defective gene from each carrier parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of MPS VI children will be carriers.
There is no cure, but treatments such as enzyme replacement therapies can help make MPS VI a more manageable disease. In June 1, 2005, the U.S. Food and Drug Administration (FDA) granted marketing approval for Naglazyme (galsulfase), the first enzyme replacement therapy approved for the treatment of MPS VI.
MPS VII is a mucopolysaccharide disease also known as Sly syndrome. It takes its name from Dr. William Sly who originally described the condition in 1972.
Mucopolysaccharides are chains of sugar molecules used to build connective tissues in the body.
The body constantly replaces used materials and breaks them down for disposal. Patients with MPS VII are missing the enzyme beta-glucuronidase, which is essential to breaking down the mucopolysaccharides heparan sulfate, chondroitin 4-, 6-sulfates, and dermatan sulfate. These materials remain stored in the body’s cells, causing progressive damage. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
MPS VII is estimated to occur in 1 in 250,000 newborns. It is one of the rarest types of mucopolysaccharidosis.
MPS VII is caused by a recessive gene. There is a one in four chance with every pregnancy that the child will inherit the defective gene from each carrier parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of Sly patients will be carriers.
Although originally thought to be two separate diseases, ML II and ML III are both caused by deficiencies of a targeting enzyme and are variations of the same disease. Individuals with more severe features have ML II; those with less severe, or attenuated, features have ML III.
The body constantly replaces used materials and breaks them down for disposal. This activity happens in the lysosomes of the cells. Enzymes responsible for breaking down the used materials can only reach the lysosome after a special signal has been attached to them. In ML II and ML III, the signal is not attached and the enzymes fail to reach the cell. The enzyme responsible for attaching the targeting signal is phospho-N-acetylglucosamine-transferase.
The cells filled with storage material are known as “inclusion cells,” hence the name “I-Cell” disorder. Babies may show little sign of the disease, but as cells sustain damage, symptoms start to appear.
These diseases are very rare and sometimes misdiagnosed, so it is difficult to give accurate figures on frequency. The current estimate is that two or three individuals per 1 million births are diagnosed with ML II and ML III.
I-Cell and Pseudo-Hurler syndrome are caused by a recessive gene. There is a one in four chance with every pregnancy that the child will inherit the defective gene from each carrier parent and will be affected with the disease. There is a two in three chance that unaffected brothers and sisters of an individual with ML will be carriers.
At present there is treatment for symptoms as they arise but no cure for the underlying condition. Various experimental methods have been used to try to replace the missing enzyme, but none so far has been of any significant long term benefit.
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