Duarte galactosemia (DG or D/G galactosemia)


Duarte galactosemia (DG or D/G galactosemia) is an inherited condition which affects a special enzyme needed to break down a sugar that is part of all milk products and several other foods, including breast milk and most formulas. DG is a milder type of galactosemia and does not have the same medical complications as classic or other types of galactosemia. An individual with DG is only missing some of the enzyme that breaks down the milk sugar known as galactose. A person with DG has more enzyme than a person with Classic galactosemia. Early treatment and monitoring is important for infants with this condition. Some children with DG manage the condition with a special diet low in the milk sugars, lactose and galactose. Often, children are on the diet only for the first year of life. Some children with DG do not need a special diet at all.

All types of galactosemia are passed on, or inherited, through instructions in the body called genes. A child gets two copies of all genes in the body, one copy from the mother and the other copy from the father. One of our genes gives the instructions to make the enzyme needed to break down galactose. If a child received two copies of this gene that are not working properly, he or she will have galactosemia. DG is caused when a person inherits either one copy of the Classic galactosemia gene (G) and one copy of the Duarte gene (D), or two copies of the Duarte gene (DD). If a person inherits a normal copy of the gene (N) and a copy of the Duarte gene (D), then he or she is a carrier for DG. Carriers do not have symptoms of galactosemia, but they can pass on the Duarte gene to their children.

The amount of enzyme a person has depends on the genes that they have. The table below shows the different possibilities.

Genes Amount of Enzyme Type of Galactosemia Treatment
N and N 100% Unaffected None
N and D 75% Duarte galactosemia carrier None
N and G 50% Classic galactosemia carrier None
D and D 50% Duarte galactosemia Typically no special diet
D and G 25-50% Duarte galactosemia May or may not be treated with special diet
G and G Less than 5% Classic galactosemia Needs special diet

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