Males and females are affected equally. The disease was discovered in 1934 by Ivar Asbjørn Følling, with the importance of diet determined in 1935. Gene therapy, while promising, requires a great deal more study as of 2014. Signs and symptoms
Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also result in a musty smell and lighter skin. A baby born to a mother who has poorly treated PKU may have heart problems, a small head, and low birth weight.Because the mothers body is able to break down phenylalanine during pregnancy, infants with PKU are normal at birth. The disease is not detectable by physical examination at that time, because no damage has yet been done. Newborn screening is performed to detect the disease and initiate treatment before any damage is done. The blood sample is usually taken by a heel prick, typically performed 2–7 days after birth. This test can reveal elevated phenylalanine levels after one or two days of normal infant feeding.If a child is not diagnosed during the routine newborn screening test and a phenylalanine-restricted diet is not introduced, then phenylalanine levels in the blood will increase over time. Toxic levels of phenylalanine (and insufficient levels of tyrosine) can interfere with infant development in ways that have permanent effects. The disease may present clinically with seizures,  hypopigmentation (excessively fair hair and skin), and a "musty odor" to the babys sweat and urine (due to phenylacetate, a carboxylic acid produced by the oxidation of phenylacetone).
A 1987 study from Slovakia reports a Roma population with an extremely high incidence of PKU (one case in 40 births) due to extensive inbreeding. It is the most common amino acid metabolic problem in the United Kingdom. History
Before the causes of PKU were understood, PKU caused severe disability in most people who inherited the relevant mutations. Nobel and Pulitzer Prize winning author Pearl S. Buck had a daughter named Carol who lived with PKU before treatment was available, and wrote an account of its effects in a book called The Child Who Never Grew. Many untreated PKU patients born before widespread newborn screening are still alive, largely in dependent living homes/institutions.Phenylketonuria was discovered by the Norwegian physician Ivar Asbjørn Følling in 1934 when he noticed hyperphenylalaninemia (HPA) was associated with intellectual disability. In Norway, this disorder is known as Føllings disease, named after its discoverer. Følling was one of the first physicians to apply detailed chemical analysis to the study of disease. In 1934 at Rikshospitalet, Følling saw a young woman named Borgny Egeland. She had two children, Liv and Dag, who had been normal at birth but subsequently developed intellectual disability. When Dag was about a year old, the mother noticed a strong smell to his urine. Følling obtained urine samples from the children and, after many tests, he found that the substance causing the odor in the urine was phenylpyruvic acid.