Genetics

Galactosemia is a recessive trait, which means it is only expressed if a person carries two galactosemia alleles. It is extremely rare: about 1 in 30,000-60,000 people inherit galactosemia, and there are only 9,066 people with the disorder in the United States. There are three main types of galactosemia: type 1 (deficient GALT enzyme), type 2 (deficient GALK enzyme), and type 3 (deficient GALE enzyme). These three enzymes all break down the galactose found in milk products. The most common type is type 1, however they are all very rare.