The total or nearly total deficiency of the GALT enzyme threatens life, and if not treated, a patient may develop complications such as sepsis, liver failure, mental retardation, or even death. Several mutations that cause this disease are common in people with G/G genotype of the classic galactosemia (Williams & Wilkins 563).
The real name of this gene is galactokinase 1. The GALKI gene gives instructions for making galctokinase 1 enzyme. This enzyme is responsible for enabling the body to process galactose, a simple sugar present in almost all dairy products and numerous baby formulas (Leonard 101). Over 20 mutations in the GALKI gene are present in patients with galactosemia. Most of the mutations alter the amino acids in galctokinase or delete some genetic material from the GALKI gene leading to an unsteady or inactive form of this enzyme.
Classic galactosemia is a genetic disorder resulting from mutations in the GALT gene. Persons must inherit two harmful copies of this gene, at least one from each parent. Whereas over 170 mutations that cause diseases have been identified to cause classical galactosemia of the genotype GG, only a few have been commonly reported. They include:
This mutation accounts to approximately 54 to 70% of the alleles in the classic galactosemia. S135L is the pathogenic mutation that is most reported in African Americans, making about 50% of the distorted alleles of the total population. In Eastern Europe, K285N mutation is accounts for only 8% of the classic galacttosemia in the general population in Europe (Leonard 102).
The D mutation is reportedly present in the United States with only 5% of the whole population. Enzyme activity is almost 50%of usual DD homozygote and is adequate such that these people do not have biochemical or clinical characteristics of glactosemia. Duarte galactosemia or sometimes called DG compound heterozygote express noticeably limited enzyme activity of close to 25%