This congenital disease is first and foremost caused by an enzymatic failure; i.e. a lack of phenylalanine hydroxylase which is responsible for the transformation of the amino acid phenylalanine into tyrosine. However, there are many forms of PKU and the biochemical picture is far more detailed than this outline and also partly unclear.
Today, screening at birth and rational nutritional treatment during adolescence - first and foremost through a large reduction in the consumption of phenylalanine - save most children from mental and physical degeneration and early death which has been the destiny for most people in the history of mankind suffering from this disease. Nowadays, the disease can be kept under control.
