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Galactosemia is a rare genetic metabolic disorder which affects an individual's ability to properly digest galactose. Lactose in food (such as dairy products) is broken down by the body into glucose and galactose. Normally, galactose is then converted into glucose by the enzyme GALT. In individuals with galactosemia, GALT activity is severely diminished. This can cause toxic levels of galactose to build up in the blood, resulting in enlarged liver, renal failure, cataracts, and brain damage. Without treatment, as high as 75% of infants with galactosemia will die.
There are two variants of the gene responsible for galactosemia. One variant causes so-called classic galactosemia, in which GALT activity is nearly zero and the most serious effects are prominent. The variant gene, responsible for Duarte galactosemia, causes GALT activity about half of normal levels. Individuals with Duarte galactosemia may experience few or none of the serious effects of classic galactosemia. This is dependent on a number of factors, but most important is the amount of lactose and galactose in the diet. It is also possible for a person to have one each of the classic and Duarte genes, in which case GALT activity is intermediate.
Galactosemia is now routinely screened for in infants within the USA. Consequently, individuals may be diagnosed early. The most important treatment for galactosemia is a carefully restricted diet. Until recently, it was thought that individuals who were diagnosed with galactosemia early and put on restricted diets could escape the negative effects entirely. Recent study has shown that this is not the case; many galactosemia patients diagnosed as infants show long term effects such as learning disabilities.
Galactosemia should not be confused with lactose intolerance. Lactose intolerant individuals may consume dairy products, although they will likely experience unpleasant abdominal symptoms; individuals with galactosemia should not consume products containing lactose at all.
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