Phenylketonuria
From Conservapedia
Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder that causes a deficiency in the enzyme phenylalanine hydroxylase. This enzyme normally metabolizes the amino acid phenylalanine into the amino acid tyrosine. If left untreated, the condition causes a build-up of phenylalanine in the tissues, which can lead to brain damage. If caught early, it can be controlled by a diet low in phenylalanine and high in tyrosine. There is no known cure.