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Mucopolysaccharidoses

By

Matt Demczko

, MD, Mitochondrial Medicine, Children's Hospital of Philadelphia

Medically Reviewed Dec 2021 | Modified Sep 2022
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Topic Resources

Mucopolysaccharidoses are a type of lysosomal storage disorder Overview of Lysosomal Storage Disorders Lysosomal storage disorders are hereditary metabolic disorders. Hereditary disorders occur when parents pass the defective genes that cause these disorders on to their children. There are different... read more in which complex sugar molecules are not broken down normally and accumulate in harmful amounts in body tissues. The result is a characteristic facial appearance and abnormalities of the bones, eyes, liver, and spleen, sometimes accompanied by intellectual disability. Mucopolysaccharidoses occur when parents pass the defective genes Genes Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells... read more Genes that cause these disorders on to their children.

  • Mucopolysaccharidoses occur when the body lacks enzymes needed to break down and store complex sugar molecules.

  • Typically, symptoms include short stature, hairiness, stiff finger joints, and coarseness of the face.

  • The diagnosis is based on symptoms, a physical examination, and blood tests.

  • Although a normal life span is possible, some types cause premature death.

  • Treatment may include lifelong enzyme replacement therapy, and sometimes a bone marrow transplant.

There are different types of inherited disorders Inheritance of Single-Gene Disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more . In many hereditary metabolic disorders, both parents of the affected child carry a copy of the abnormal gene. Because usually two copies of the abnormal gene are necessary for the disorder to occur, usually neither parent has the disorder. Some hereditary metabolic disorders are X-linked X-Linked Recessive Disorders X-Linked Recessive Disorders , which means only one copy of the abnormal gene can cause the disorder in boys. (See also Overview of Hereditary Metabolic Disorders Overview of Hereditary Metabolic Disorders Hereditary metabolic disorders are inherited genetic conditions that cause metabolism problems. Heredity is the passing of genes from one generation to the next. Children inherit their parents'... read more .)

Complex sugar molecules called mucopolysaccharides (glycosaminoglycans) are essential parts of many body tissues. In mucopolysaccharidoses, the body lacks enzymes needed to break down (metabolize) and store mucopolysaccharides. As a result, excess mucopolysaccharides enter the blood and are deposited in abnormal locations throughout the body.

Types of mucopolysaccharidosis

There are many types of mucopolysaccharidosis depending on which specific enzyme is missing. The types are classified by Roman numerals and sometimes also given a specific name (for example, Hurler syndrome and Hunter syndrome).

Symptoms of Mucopolysaccharidoses

Different types of mucopolysaccharidosis have slightly different symptoms but, in general, during infancy and childhood, short stature, hairiness, and abnormal development become noticeable. The face may appear heavy with a large head, prominent forehead, short nose, and large lips and tongue. Some types of mucopolysaccharidoses cause intellectual disability Intellectual Disability Intellectual disability is significantly below average intellectual functioning present from birth or early infancy, causing limitations in the ability to conduct normal activities of daily... read more that may worsen over the course of a person's life. In some types, vision or hearing may become impaired. The arteries or heart valves can be affected. Finger joints are often stiff.

Table

Diagnosis of Mucopolysaccharidoses

  • Prenatal screening tests

  • Based on symptoms and an examination

  • Bone x-rays

  • Sometimes imaging or other blood tests

After birth, a doctor usually bases the diagnosis of mucopolysaccharidoses on the symptoms and a physical examination. The presence of a mucopolysaccharidosis in other family members also suggests the diagnosis. Urine tests may help but are sometimes inaccurate. X-rays may show characteristic bone abnormalities. Mucopolysaccharidoses also are diagnosed by analyzing blood cells. Genetic testing Genetic Screening Before Pregnancy Genetic screening is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder. Hereditary genetic disorders are disorders of chromosomes or... read more to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder is available.

Prognosis for Mucopolysaccharidoses

The prognosis depends on the type of mucopolysaccharidosis. A normal life span is possible. Some types, usually those that affect the heart, may cause premature death.

Treatment of Mucopolysaccharidoses

  • Enzyme replacement

  • Sometimes bone marrow or stem cell transplantation

Lifelong enzyme replacement therapy is being used to treat some mucopolysaccharidoses and may prevent the disorders from getting worse and reverse some of the complications.

More Information

The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

NOTE: This is the Consumer Version. DOCTORS: VIEW PROFESSIONAL VERSION
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