The condition known as phenylketonuria ( phenylpyruvic oligophrenia) falls within the group of "inborn errors of metabolism." It was first described in 1934 by a Norwegian biochemist, Foiling. Clinically, this error is expressed by a severe degree of mental defect, the excretion of a strongly aromatic urine, and in some patients a lightening in the color of the hair, skin, and eyes. Biochemically, the disease is characterized by failure to oxidize phenylalanine, an essential amino acid, to tyrosine and by the excretion of phenyl acids in the urine. One of these, a phenyl-keto compound, phenylpyruvic acid, is found in large amounts in the urine; hence the name, phenylketonuria. This compound gives a characteristic color reaction when ferric chloride or 2,4-dinitrophenylhydrazine is added to the urine. These are simple tests and, when positive, are usually diagnostic of phenylketonuria.
Early identification of the affected individual is important for several reasons. Phenylketonuria is one
Wright SW. PHENYLKETONURIA. JAMA. 1957;165(16):2079–2083. doi:10.1001/jama.1957.72980340006012
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