Galactosemia
From Wikipedia, the free encyclopedia
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|---|---|
| Galactose | |
| ICD-10 | E74.2 |
| ICD-9 | 271.1 |
| OMIM | 230400 230200 230350 |
| DiseasesDB | 5056 29829 29842 |
| MeSH | D005693 |
Galactosemia is a rare genetic metabolic disorder which affects an individual's ability to properly digest the sugar galactose.
Goppert first described the disease in 1917.[1]
Its incidence is about 1 per 47,000 births (classic type). It is much rarer in Japan.
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[edit] Cause
Lactose in food (such as dairy products) is broken down by the body into glucose and galactose.
In individuals with galactosemia, the needed enzymes are severely diminished, leading to toxic levels of galactose to build up in the blood, resulting in hepatomegaly (an enlarged liver), renal failure, cataracts, and brain damage. Without treatment, mortality in infants with galactosemia is about 75%.
[edit] Types
[edit] Type 1
Galactose is converted into glucose by the action of three enzymes, known as the Leloir pathway. These include Galactokinase, galactose-1-phosphate uridyl transferase (GALT), and UDP-galactose 4-epimerase. A deficiency in GALT is the most common cause of galactosemia.
There are two variants of the GALT gene responsible for galactosemia.
- One variant causes so-called classic galactosemia, in which there is an extreme deficiency in galactose-1 phosphate uridyltransferase. It is an autosomal recessive condition. The gene for GALT was mapped at 9p13. Most serious conditions are prominent.
- The variant gene, responsible for Duarte galactosemia, leads to about half the normal levels of GALT. Individuals with Duarte galactosemia may experience few or none of the serious symptoms of classic galactosemia.
The severity of the symptoms is dependent on a number of factors, most importantly the amount of lactose in the individual's diet. It is also possible to have one each of the classic and Duarte genes, in which case GALT activity is intermediate.
[edit] Types 2 and 3
Type 2 galactosemia is caused by deficiencies of galactokinase.
Type 3 galactosemia is caused by deficiencies of UDP galactose epimerase.
[edit] Diagnosis
Infants are now routinely screened for galactosemia in the United States, and the diagnosis is made while the person is still an infant.
[edit] Treatment
The only treatment for classic galactosemia is eliminating lactose and galactose from the diet. Even with an early diagnosis and a restricted diet, however, some individuals with galactosemia experience long-term complications such as learning disability, and in girls, ovarian failure. Such complications have not been associated with Duarte galactosemia, and many individuals with Duarte galactosemia do not need to restrict their diet at all. Infants with classic galactosemia cannot be breast-fed due to lactose in human breast milk and are usually fed a soy-based formula.[2]
Galactosemia is sometimes confused with lactose intolerance, but galactosemia is a more serious condition. Lactose intolerant individuals have an acquired or inherited shortage of the enzyme lactase, and experience abdominal pains after ingesting dairy products, but no long-term effects. In contrast, a galactosemic individual who consumes galactose can cause permanent damage to their bodies.
For a thorough scientific overview of galactosemia, one can consult chapter 72 of OMMBID[3]. For more online resources and references, see inborn error of metabolism.
[edit] Reference
- ^ Goppert F. Galaktosurie nach Milchzuckergabe bei angeborenem, familiaerem chronischem Leberleiden. Klin Wschr 1917;54:473-477.
- ^ http://www.cdc.gov/breastfeeding/disease/contraindicators.htm
- ^ Charles Scriver, Beaudet, A.L., Valle, D., Sly, W.S., Vogelstein, B., Childs, B., Kinzler, K.W. (2006). The Online Metabolic and Molecular Bases of Inherited Disease. New York: McGraw-Hill. - Free summaries of 255 chapters, full text through many universities and organizations. Also, the OMMBID blog.
[edit] External links
- Galactosemia Resources and Information
- Parents of Galactosemic Children, Inc. website
- What is Galactosemia?
