Inherited metabolic storage disorders are a group of inherited diseases in which the lack of an enzyme affects various organs and tissues, including the brain. Enzymes are proteins that play many roles, including to metabolize (break down) substances in the body.
In metabolic storage disorders, the body lacks an enzyme needed to metabolize a substance, such as a sugar. Instead, the substance builds up in the body, where it can damage the brain, nervous system, bones, organs and other tissues. Different metabolic disorders affect different enzymes and cause different types and levels of damage.
Metabolic storage disorders are caused by a mutation (mistake) in a gene that affects metabolism. Genes carry an inherited code of instructions that tells the body how to make every cell and substance in the body.
These disorders are rare. Many of them appear in childhood, although some can also appear in adults. A bone marrow or cord blood transplant (also called a BMT) is a treatment option for some of these disorders.
Mucopolysaccharidoses, also called MPS disorders, are a subgroup of metabolic disorders. Some MPS disorders have been treated with transplant:
- Hurler's syndrome (MPS I) — this is the form of MPS that doctors have the most experience treating with transplant, since 1980
- Maroteaux-Lamy syndrome (MPS VI)
- Sly syndrome (MPS VII)
Leukodystrophies are another subgroup of metabolic disorders, some of which have been treated with transplant:
Other metabolic disorders have also been treated with transplant. For most of these disorders, experience with transplant is limited.
- Gaucher disease
- Mucolipidosis II (I-cell disease)
- Wolman syndrome
If you or a family member has an inherited metabolic storage disorder, it is important to talk to a doctor who has experience treating the disorder. These disorders are rare and complex. Early diagnosis and prompt treatment are important. If your doctor has not treated other patients with your disorder, ask him or her to refer you to an expert for consultation. A doctor with experience treating the disorder can discuss whether transplant is a treatment option for you or your family member.
Paul Orchard, M.D., University of Minnesota BMT Program at Fairview University Medical Center, Minneapolis, Minn.
Charles Peters, M.D., Sanford Children's Specialty Clinic, Sioux Falls, S.D.