Effective, Low-Cost Screening of Newborns Eliminates a Major
Cause of Intellectual Disability In 1934, Norwegian Dr. Asbjörn
Fölling discovered PKU, a rare disease that, if left untreated
in newborns, caused intellectual disability, seizures, and
deafness. In 1939, research showed that PKU was an inherited
disorder that resulted from the body's inability to break down
(metabolize) the amino acid phenylalanine (Phe), a common part
of many proteins. The extra Phe, left in its original form and
not broken down, built up in the blood and body tissues and
prevented normal brain development, which often resulted in
intellectual disability. Through his efforts to understand PKU,
Dr. Fölling discovered that a certain chemical called
phenylpyruvic acid, which was present in the urine of people
with untreated PKU, turned green in the presence of another
chemical, ferric chloride. This reaction provided the first test
for PKU. Most infants, only a few days old, did not have enough
of the chemical in their urine for the