Galactosemia

Galactosemia is an autosomal recessive disorder of galactose metabolism. Normally, lactose, the major carbohydrate of mammalian milk, is split into glucose and galactose in the intestinal microvilli by lactase. Galactose is then converted to glucose in three steps. Two variants of galactosemia have been identified. In the more common variant, there is a lack of galactose-1-phosphate uridyl transferase involved in reaction 2. The rare variant arises from a deficiency of galactokinase, involved in reaction 1.