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1934. – The Year Of The World’s First PKU Test

As we previously wrote, Norwegian doctor Ivar Asbjørn Følling became world famous after he discovered the Phenylketonuria (PKU) disorder in 1934. However, not too many people are familiar with the methods he used to discover this disorder, and ultimately save and improve life quality of millions of children worldwide.

In 1934. Dr. Følling received the mother of two children who developed various forms of mental retardation. Both of the kids, older daughter Liv and son named Dag, were born perfectly normal, but none of the doctors couldn’t determine the main reason of their retardation. Dr. Følling immediately knew he couldn’t help those children, but he was determined to find the main cause of their condition and to help other children in future.

After the initial test that showed no trace of glucose or protein in children’s urine sample, Dr. Følling turned his attention towards searching abnormal substances, in this case – ketones. He added a certain amount of ferric chloride solution in the urine sample, but the unusual chemical reaction that followed, surprised even experienced Dr. Ivar Asbjørn Følling.

Instead of red-brown urine color reaction and ketones discovery, the girls’ urine sample assumed a dark-green color which faded in a few minutes. Repeated tests after two weeks gave Dr. Følling the same results, which further intrigued him to finally find and isolate the main source of this unusual chemical reaction.

Many more analysis and six recrystalizations later, Dr. Følling was on verge of historical discovery after he isolated the single acidic material, which had nine carbons, eight hydrogen and three oxygen atoms (9C, 8H, 3O). That same material gave benzaldehyde and benzoic acid after stronger oxidation, leading him to conclusion that the isolated substance he was looking for was phenylpyruvic acid.

After he discovered the main cause of retardation in Liv and Dag’s case, Dr. Følling tested further 430 mentally retarded children. Of those 430 children, he found eight more children with the same symptoms, including one pair of twins. Few years later, after Dr. Lionel Penrose advice, this disorder finally got the official name – Phenylketonuria – due to phenylketone, phenylpyruvic acid discovered in children’s urine samples.

Want to learn more?


“The PKU Paradox: A Short History of a Genetic Disease” by Diane B. Paul and Jeffrey P. Brosco.

“Robert Guthrie–The Pku Story: Crusade Against Mental Retardation” by Jean Holt Koch.

“Low Protein Cookery for Phenylketonuria” by Virginia E. Schuett.

“Low Protein Food List for PKU” by Virginia E. Schuett.

“Low Protein Bread Machine Baking for PKU” by Virginia E. Schuett.

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