, which means “galactose in the blood”, is a rare inherited condition. People with galactosemia have problems digesting a type of sugar called galactose from the food they eat. Because they cannot break galactose down properly, it builds up in their blood. Galactose is found in milk and all foods that contain milk. Galactosemia occurs when an enzyme, called ‘galactose-1-phosphate uridyl transferase’ (GALT), is either missing or not working properly. Without enough GALT enzyme activity, galactose cannot be changed to glucose so it builds up in the blood in large amounts.
There are different types of galactosemia: classic galactosemia (also known as type I and is the most common and most severe form of the condition), galactosemia type II (also called galactokinase deficiency), and type III (also called galactose epimerase deficiency). The different types of galactosemia is caused by mutations in the GALT, GALE, and GALK1 genes and is inherited in an autosomal recessive fashion.
Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.