Differentiating MPS I

Findings in MPS I may overlap with those of other lysosomal storage disorders, particularly other mucopolysaccharide diseases, including multiple sulfatase deficiency. Detailed clinical findings and biochemical testing is critical for distinguishing among them.

Some diseases that may resemble MPS I include:

• MPS II, or Hunter syndrome: Hunter syndrome patients exhibit many of the same clinical features as MPS I patients, including coarse facial features, sight and hearing difficulties, respiratory infections, mental retardation, bone deformities, joint stiffness, heart disease, and enlarged organs. Unlike MPS I, Hunter syndrome is caused by a lack of the enzyme iduronate sulphate sulphatase and generally only affects males.^[1]
• Mucolipidosis (ML) III, or Pseudo-Hurler polydystrophy: This disease is a form of mucolipidosis, a condition in which the enzyme phosphotransferase is missing from the lysosome and is instead found in excessive amounts in the blood. ML III resembles a mild form of MPS I, with clinical features such as enlarged organs, gastrointestinal problems, respiratory infections, heart disease, joint stiffness, corneal clouding,
  and skeletal abnormalities.^[2]
• Multiple sulfatase deficiency: Multiple sulfatase deficiency is a very rare hereditary metabolic disorder in which all of the known sulfatase enzymes (thought to be 7 in number) are deficient or inoperative. Major symptoms include mildly coarsened facial features, deafness, and an enlarged liver and spleen. Abnormalities of the skeleton may occur, such as curvature of the spine and the breast bone. The skin is usually dry and scaly. Before symptoms are noticeable, children with this disorder usually develop more slowly than normal. They may not learn to walk or speak as quickly as other children.^[3]

References:

1. The Australian MPS Society. Available at:
http://www.mpssociety.org.au
Accessed on January 11, 2006.

2. The Australian MPS Society. Available at:
http://www.mpssociety.org.au
Accessed on January 11, 2006.

3. National Organization for Rare Diseases. Available at:
http://www.rarediseases.org
Accessed January 11, 2006.