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Enzyme Deficient Diseases: Galactosaemia

Year 11 Biology

Galactosaemia Foundation

Galactosemia was first "discovered" in 1908. Von Ruess, in a 1908 publication entitled, "Sugar Excretion in Infancy," reported on a breast-fed infant with failure to thrive, enlargement of the liver and spleen, and "galactosuria". This infant ceased to excrete galactose through the urine when milk products were removed from the diet.


Classical galactosaemia is an inborn error of galactose metabolism which may lead to impairments in body functions and accordingly, need for additional care. The primary aim of this study was to establish the type and intensity of this additional care.


Existing longitudinal data on patients with classical galactosaemia s u g g e s t s that neurocognitive functioning is impaired and, in isolated case reports, may show a decline in performance over time.



Galactosemia is a rare, hereditary disorder of carbohydrate metabolism that affects the body's ability to convert galactose (a sugar contained in milk, including human mother's milk) to glucose (a different type of sugar).


Lesson on galactose absorption, metabolism via the Leloir pathway, and the medical condition known as galactosemia. Galactose is monosaccharide, which is typically ingested in the form of lactose (galactose + glucose) or free galactose in certain fruits and vegetables. Upon ingestion and digestion, the galactose is transported into an intestinal endothelial cell through SGLT1 and transported into the blood via GLUT2. Upon entry into a receiving cell, galactose is metabolized by the Leloir pathway to form glucose-6-phosphate, which can be rerouted and utilized in the glycolysis pathway to form ATP and pyruvate. If there are any congenital issues causing deficiency in one of three enzymes in the Leloir pathway, this can lead to dysfunctional galactose metabolism and subsequent high blood levels of galactose, leading to issues with red blood cell functioning and increasing risk of cataract formation.



Classic galactosemia is an autosomal recessive disorder of galactose metabolism.

Handbook for Galactosaemia

Galactosaemia is an inherited condition that affects how the body processes a type of sugar called galactose. Galactose is an essential part of some structures within the body, and our bodies make some galactose themselves. Galactose is also part of lactose, the main sugar in all animal milks. (Including breast milk, most infant formulas, cow's milk, goat’s and sheep’s milk.


We report a child with classical galactosaemia whose diagnosis was missed until 12 weeks of age. The limitations of urine screening tests are discussed and the wider use of a qualitative enzyme assay for screening is recommended. Reference ranges for a quantitative enzyme assay using 14galactose-1-phosphate as substrate are presented.




The Australian Galactosaemia Support Network is a non-profit institution set up to support the treatment of galactosaemia.