Updated: 11-05-2025
Phenylketonuria – Symptoms, Diagnosis, and Treatment
It is a rare type of genetic disorder in which the body becomes incapable of breaking down the essential amino acid phenylalanine.
These are the building blocks made up of protein.
Phenylketonuria is an important substance present in all the proteins.
It is also present in some types of artificial sweeteners.
The human body makes use of the enzyme phenylalanine hydroxylase for the conversion of phenylalanine into tyrosine, which is a nonessential amino acid.
Tyrosine is essential for your body as it makes neurotransmitters such as norepinephrine, epinephrine, and dopamine.
In the absence of treatment for PKU, a large amount of phenylalanine builds up inside the body and can lead to damage to the brain and nervous system.
Symptoms of Phenylketonuria
The symptoms of phenylketonuria range from severe to mild.
- The highest level of symptoms is visible in a condition known as classic PKU.
- An untreated child suffering from PKU can develop symptoms including stunted growth, hyperactivity, seizures, mental retardation, intellectual disabilities, eczema, distinct urine, skin, or breath odour (musty smell), and lightening of hair, skin, and eye colour.
- Less severe phenylketonuria is known as non-PKU or variant PKU.
Diagnosis/Tests of Phenylketonuria
- Blood sample testing has been prevalent since the 1960s for detecting PKU genetic disorders.
- To prevent the negative result, the screening is done after the baby has taken milk for at least one day.
- If the carers suspect the presence of this disorder, other genetic and blood tests are recommended to confirm the first result and to detect the presence of the PAH gene mutation that causes PKU.
- These tests are carried out within the first six weeks of the birth of the baby.
Treatment for Phenylketonuria
- The main part of the treatment for PKU is eating a diet especially prescribed for treating this disorder.
- The dietitian will recommend a diet that limits your intake of phenylalanine-containing foods, especially proteins.
- A special PKU formula is included in the diet so that the patient receives a regular supply of adequate proteins needed by the body.
- This formula is a special type of medical food that has amino acids.
- It is important for a person suffering from this type of genetic disorder to keep on consuming this PKU formula throughout their life so that the symptoms can be managed.
From young children to adults, everyone is advised to keep up this strict diet so that their health and mental functioning remain stable.
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