Mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of inherited disorders. These disorders are rare. In general, males and females are equally affected. Both parents must be carriers to have an affected child.

With these disorders, over time, a chemical builds up in the cell. This buildup changes a person's appearance and causes progressive damage in the bones and joints, the liver, the eyes, and the brain. Eventually the organs of the body enlarge and slowly stop working. In some cases, it can lead to death. Seven clinical types of the disorders have been found. This information will cover 6 of the 7 types:

  • MPS I.

  • MPS II.

  • MPS III.

  • MPS IV.

  • MPS VI.

  • MPS VII.

In general, patients with MPS have a period of normal development in childhood, followed by a decline in physical function or mental function or both as the amount of stored material overwhelms cell function in various organs. Treatment with bone marrow or stem cell transplantation and enzyme replacement are available for some types of MPS.

FEATURES OF THE COMMON TYPES OF MPS

MPS I

There are 3 different subtypes of MPS I:

  • Hurler syndrome (MPS I H). Hurler syndrome is the most severe form of the disorder. It occurs in infancy. Symptoms include clouding of the cornea and progressive physical and mental disability. Hearing loss and heart valve disorders are common. Coarsening of the facial features is noticed in the first 2 years. By age 3 years, growth ceases. Death usually occurs before age 10.

  • Scheie syndrome (MPS I S). Patients with Scheie syndrome have milder symptoms and normal intelligence.

  • Hurler/Scheie syndrome(MPS I H/S). Those with Hurler/Scheie syndrome have intermediate symptoms.

MPS II

Mucopolysaccharidosis II is also called Hunter syndrome. Hunter syndrome affects males primarily. Females are usually unaffected carriers of the disorder and can pass the condition on to their sons. It usually affects juveniles but the age of onset and severity varies considerably. There are 2 kinds MPS II:

  • Mucopolysaccharidosis II A is the severe form. Symptoms of this severe form are:

  • Bone changes and joint stiffness.

  • Large head.

  • Progressive mental deterioration.

  • Progressive airway disease.

  • Short stature.

  • Progressive deafness.

  • Progressive heart disease.

  • Bone changes and joint stiffness.

  • Large head.

  • Death usually occurs by age 15 years.

  • Mucopolysaccharidosis II B is the mild form. Symptoms of this form are:

  • Short stature.

  • Limited motion of the joints.

  • Enlarged liver or spleen or both.

  • Enlarged head, lips, and tongue.

  • Misaligned teeth.

  • Hoarse voice.

In the milder form, intelligence may be normal, and survival to the early adult years is common.

MPS III

Patients with MPS III, or Sanfilippo syndrome, have progressive dementia and mental deterioration in childhood. There are 4 subtypes: MPS III A-D. Death usually occurs in the late teens.

MPS IV

MPS IV is also called Morquio syndrome. There are 2 types: MPS IVA and MPS IVB. Symptoms usually appear in infancy. They may include severe dwarfing and corneal clouding. Intelligence is normal. Cardiac or respiratory disease may cause death in the third or fourth decade of life.

MPS VI

MPS VI is also called Maroteaux-Lamy syndrome. It resembles Hurler syndrome, but intelligence is normal. Onset is in infancy, with an early symptom being late onset of walking. By age 10 years, the trunk is short and movement of the joints is restricted. Individuals may live into the second or third decade.

MPS VII

MPS VII is also called Sly disease. It is one of the least common forms of MPS. Symptoms may include:

  • Swelling of the body tissues at birth (hydrops fetalis).

  • Corneal clouding.

  • Hydrocephalus (enlargement of the fluid-filled spaces in the brain).

  • Short stature.

  • Skeletal irregularities.

  • Enlargement of the liver and spleen.

  • Impaired movement of the joints.

  • Intellectual impairments vary for this type of MPS.

DIAGNOSIS

Any of the types of MPS can be diagnosed based on a physical exam and urine test results. Prenatal diagnosis is also available.

TREATMENT

There is no cure for any of these disorders. Treatment is symptomatic and supportive. The outcome varies depending on the type of MPS. Surgery to remove tonsils and adenoids may help people who have breathing disorders, especially during sleep. In several individuals, bone marrow and umbilical cord blood transplants have been attempted, with varying degrees of success. Enzyme replacement therapy has had modest effect in improving the non-neurologic aspects of some forms of MPS.

FOR MORE INFORMATION

National MPS Society: www.mpssociety.org

Mucopolysaccharidoses Fact Sheet: www.ninds.nih.gov/disorders/mucopolysaccharidoses/detail_mucopolysaccharidoses.htm