Disease Etiology 

Classic galactosemia is an autosomal recessive inherited disorder that inhibits energy production from galactose (1). Because the body is unable to metabolize galactose via the Leloir pathway, hypergalactosemia occurs (1). Classic galactosemia is caused by a deficiency of the galactose-1-phosphate uridylyltransferase (GALT) enzyme, the second enzyme in the Leloir pathway (2). A lack of this enzyme causes a buildup of galactose-1-phosphate and other galactose metabolites.