Galactosemia occurs in two very different clinical forms. Deficiency of galactokinase produces very mild disease with the only significant complication being cataract formation. In contrast, homozygous deficiency of galactose-1-phosphate uridyltransferase produces severe disease culminating in death in infancy. In addition to galactosemia and galactosuria, these patients have impaired renal tubular resorption leading to aminoaciduria, gastrointestinal symptoms, hepatosplenomegaly, cataracts, bleeding diathesis, hypoglycemia, and mental retardation. Pathologically, the CNS showed neuronal loss and gliosis and the liver shows fatty change progressing to cirrhosis. Benign disease with cataract formation is characteristic of galactokinase deficiency. Chronic emphysema is not associated with homozygous galactose-1-phosphate uridyltransferase deficiency, but rather with alpha 1-antitrypsin deficiency. Impaired tubular reabsorption (producing aminoaciduria) is seen within a few days or weeks of feeding milk to an infant with severe galactosemia, as opposed to chronic renal failure appearing in adolescence. Ref: Bender D.A., Mayes P.A. (2011). Chapter 21. The Pentose Phosphate Pathway & Other Pathways of Hexose Metabolism. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.