Phenylketonuria (pKU) is a rare genetic disorder in which babies are born unable to break down an amino acid called phenylalanine. This leads to the accumulation of phenylalanine. When phenylalanine levels are too high, it can damage the brain. This can lead to intellectual and developmental disabilities.

What is phenylketonuria (pKU)?

Phenylketonuria (pKU) is a rare genetic disorder in which babies are born unable to break down an amino acid called phenylalanine. This leads to the accumulation of phenylalanine. When phenylalanine levels are too high, it can damage the brain. This can lead to intellectual and developmental disabilities.

Phenylalanine is found in foods that contain protein. pKU is controllable, mostly through your diet. The key to successfully coexisting with Peking University is finding it as quickly as possible. That's why all American babies are screened for the disease at birth.

Symptoms of phenylketonuria.

Newborns are initially asymptomatic. But within a few months of birth, depending on the severity of the disease, symptoms begin to appear. These include:

smaller than normal head size (called microcephaly)

ADHD

A musty or rat-like odor on urine, breath, or skin.

Lighter skin, hair and eyes than siblings.

A twitching of the arm or leg.

Tremors or seizures.

Delayed development

Behavioral problems

Mental illness

Controlling pKU without dietary changes can lead to severe and permanent intellectual and developmental disabilities.

What is the cause of phenylketonuria?

pKU is a genetic disorder. This means that it is passed on to the baby through the parents' genes. It is caused by a mutation in a gene that helps make phenylalanine hydroxylase. This enzyme helps break down phenylalanine. When the genes are not working properly, the body cannot break down phenylalanine. It starts to accumulate and damage nerve cells in the brain.

In the United States, you are at higher risk for pKU if you are of European or Native American descent.

How is phenylketonuria diagnosed?

All newborns born in the United States are regularly tested for a range of diseases and conditions. One of these tests is blood that detects phenylalanine hydroxylase. If this enzyme is missing or if there is too much phenylalanine in the blood, more blood and urine tests are needed. These can confirm the diagnosis of pKU.

Almost all cases of pKU are diagnosed with this newborn blood test.

pKU is rarely lost during screening. Therefore, people of any age with developmental delay or intellectual disability are routinely tested for pku diet.

pKU can also be diagnosed before a baby is born. A pregnant woman can request a genetic test to see if her unborn baby has the disease. This is done with amniocentesis or chorionic villus sampling. This test may be useful if the parent already has a child with pKU. They are more likely than average to have another child with the disease.

Can phenylketonuria be prevented or avoided?

Because pKU is a genetic disease, it cannot be prevented or avoided. Genetic testing is the only way to determine if people carry the defective gene. Some people may carry the gene but not have pKU. These people are called carriers. Both parents must carry the abnormal gene in order to pass the disease to the baby.

Treats phenylketonuria.

pKU cannot be cured. The most important treatment is a diet that restricts foods containing phenylalanine. This means that the diet must be low in protein.

Newborns with this condition must use special infant formula. This can be mixed with a small amount of breast milk or regular formula. It's a delicate balance. Your baby really needs some phenylalanine to develop properly. But too much can hurt.

pKU children and adults also need to follow a low phenylalanine diet. Phenylalanine is present in most protein foods. This includes all meat and fish, milk, cheese, eggs, nuts, soy and legumes. It is also present in some non-protein foods. These include some vegetables and fruit, some bread and beer. Aspartame sweeteners release phenylalanine during digestion and must be avoided.

If you have pKU, you must follow a strict low-phenylalanine diet before and during pregnancy. The accumulation of phenylalanine can impair fetal development even if the baby does not have the genetically defective gene.

Sapropterin dihydrochloride (trade name: Kuvan) has been approved by the U.S. Food and Drug Administration for the treatment of pKU. Kuvan helps the body break down phenylalanine. However, this medicine can only help some people. It doesn't reduce enough phenylalanine, even for those who do help. People taking this drug must still eat low phenylalanine.

Living with Phenylketonuria.

Due to the very limited diet of pKU, it can be difficult to get all the essential nutrients the body needs. Special daily formulas can help people with pKU get proper nutrition. Taking supplements may also be necessary. For example, fish oil can replace some of the fatty acids (the building blocks of lipids or fats) that are lacking in standard pKU diets. These fatty acids help improve neurodevelopment.

Everyone with pKU has different levels of phenylalanine that they can tolerate. If you have pKU, you must work closely with your doctor to develop your personal eating habits. For healthy growth and development, you need to consume enough phenylalanine. However, you can't eat too much, lest it be harmful to your health. Visit your doctor often and have regular blood tests to help check everything.

pKU is very strict. But it must be followed. Babies who start a diet soon after birth usually develop normally. Many people do not show symptoms of pKU. Those who dieted throughout their lives had better overall physical and mental health than those who did not. Facing this dietary challenge, support from friends, family, or a pKU support group may be helpful.