Phenylketonuria (PKU) is a genetic disorder characterized by a buildup of phenylalanine in blood. This HealthHearty article provides a detailed account of the causes, symptoms and treatment options for this rare disorder.
Phenylketonuria (PKU) is a rare, autosomal recessive disorder, characterized by the inability to break down phenylalanine, an amino acid that is obtained through dietary proteins. This amino acid plays a vital role in the production of melanin, the pigment that influences the color of hair and skin. When this amino acid is not broken down, it gets accumulated in the tissues, as well as in blood, and affects the normal growth and development of the child.
The main cause of the PKU is a genetic mutation, that leads to partial or complete deficiency of the enzyme required for the breakdown of phenylalanine. It is an autosomal recessive disorder, and the individual is affected only if he/she inherits two defective copies of the gene, one from each parent.
If an individual inherits just one copy of the defective gene from either of the parents, he/she will not exhibit any symptoms. Such an individual is referred to as a carrier, and may or may not pass the defective gene to the next generation.
Children suffering from PKU, tend to have a lighter color of skin, hair, and eyes, as compared to their siblings. The symptoms include all or some of the following, and their intensity may vary with each individual case.
- Blue eyes and fair skin (as phenylalanine is not converted to melanin)
- Mental retardation
- Behavioral problems
- Musty odor from skin, sweat, hair, and urine
- Unusual positioning of hands
- Abnormal posture while standing
- Small head circumference
In most countries, a newborn is tested for PKU with a simple blood test called the heel stick blood test. If this PKU test comes out to be positive, more blood tests, urine tests, etc. are performed for further investigation.
When detected early, the treatment will help to arrest the disease in its mild form. The treatment requires the child to follow a strict diet to avoid high levels of phenylalanine in body. This will help to reduce the risk of mental retardation, and the child will have a better physical and mental health. The diet needs to be followed for his/her entire life. Phenylalanine is present in several protein-rich foods, as well as artificial sweeteners containing aspartame. The foods to be avoided in order to keep the levels of phenylalanine in control are:
- Beef products
Infants are advised a special formula that is free from phenylalanine. There is one FDA-approved drug that may be prescribed along with the diet.
The prognosis is good when the child is kept on a strict diet. If one delays the treatment, it may lead to irreversible brain damage. Thus, by the time the child is one year old, mental retardation becomes apparent. The children may also develop attention deficit hyperactivity disorder (ADHD).
Parents should get themselves screened for the defective PKU gene, if they are aware of its presence in any of their family members. For any further queries, speak to a genetic counselor or an appropriate health care provider.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be used as a substitute for professional medical advice.