Galactosemia also includes in rare genetic disorders that help body to break down food sugar called galactose which is normally present in milk and other dairy products. Body breaks lactose into galactose and glucose and uses these sugars for energy production. Most people with galactosemia are missing with an enzyme called GALT that helps further break down of galactose. Defects in galactose metabolism cause toxic chemicals to build up in cells of the body.
Common galactosemia is passed down in an autosomal recessive pattern. To get the disorder, a child must inherit both defective alleles from parents. Inheriting one normal gene and one mutated gene makes a person a carrier. A carrier produces less of the GALT enzyme than normal, but is still able to break down galactose and avoid having symptoms of galactosemia. However, carriers can pass the mutated gene to their children. This GALT gene is present on p arm of chromosome 9.