Galactosemia can result from a deficiency of either galactokinase or udp-glucose: galactose 1-phosphate uridylyltransferase (transferase). although a deficiency of either enzyme will cause gastric discomfort after milk ingestion, transferase deficiency also results in liver, kidney, spleen, and brain dysfunction, and in some cases, death. for each type of enzyme deficiency, identify which metabolites accumulate in the blood and tissues.

There are three types of galactosemia depending on enzyme deficiency.
1. Classic galactosemia which is an inborn autosomal recessive metabolic disorder which is caused by a deficiency of the enzyme galactose-1-phosphate uridylyltransferase. Classic galactosemia will result in accumulation of galactose-1-phosphate, galactose, and its derivatives, galactitol and galactonate.
2. Galactokinase deficiency is also an autosomal recessive metabolic disorder which results in accumulation of galactose and galactitol because conversion of galactose to galactose-1-phosphate  by galactokinase is decreased.
3. Galactose epimerase deficiency is an autosomal recessive disorder which is a result of a deficiency of the enzyme galactose epimerase. This disorder leads to the accumulation of galactose and galactose-1-phosphate.