The joy you feel when you look at your newborn baby is indescribable, right? But then, when you hear about some of the tests that are done at the hospital after the baby is born, you feel a little scared and curious. One such test is the PKU test. You may not have heard of this name. But this is a very important test. Today we are talking about this rare condition called PKU, but if identified early, it can be completely controlled and the baby can live a healthy life.
Simply put, what is PKU (Phenylketonuria)?
PKU, or Phenylketonuria, is a rare genetic disorder . It is inherited from parents. A baby with this condition cannot properly digest, or break down, the amino acid phenylalanine, which is found in the protein foods we eat.
Think of our bodies as a big factory. The food we eat is the raw materials we put into it. These raw materials are used by little workers called enzymes to make the things our bodies need. A baby with PKU has little or no production of a special enzyme called phenylalanine hydroxylase (PAH), which breaks down phenylalanine.
So what happens? Phenylalanine, which is obtained from breast milk and later from foods that the baby eats, begins to accumulate in the blood instead of being eliminated from the body. When the amount of phenylalanine that accumulates in this way increases, it becomes toxic to the baby's brain . If left untreated, this can damage the brain and cause serious complications such as intellectual disability and developmental delays.
But the best thing here is that in many countries, including Sri Lanka, hospitals perform this PKU test on every baby born. Therefore, the disease can be identified early. Since treatment can be started as soon as it is identified, the baby has the opportunity to develop normally and healthily, preventing serious symptoms from developing.
What are the symptoms of PKU?
A baby with PKU looks completely healthy at birth. So, at first, there may be no noticeable changes. If left untreated, symptoms will start to appear between three and six months of age. During this time, you may notice slight delays in your baby's development.
By the time a baby is about a year old, if left untreated, the following symptoms may become apparent.
| Symptom | Description |
|---|---|
| A strange smell | A strange, musty odor from the baby's breath, sweat, or urine. |
| Color changes | The baby's skin, hair, and eyes are lighter in color compared to the rest of the family. |
| Skin diseases | Skin diseases such as eczema. |
| Growth retardation | Weight and height not increasing in proportion to age (Growth delay). |
| Other features | Symptoms such as vomiting, nausea, and tremors. |
| Serious symptoms that can occur if left untreated | |
| Behavior problems | Frequent fidgeting, reckless behavior, and attempts to harm themselves. |
| Hyperactivity | Being too active to stay in one place. |
| Seizures | Seizure -like conditions. |
How does pregnancy affect a mother with PKU?
This is a very important point. If a woman with PKU becomes pregnant and her PKU condition is not controlled during that time, it can affect the baby in the womb. The increased level of phenylalanine in the mother's blood can harm the baby.
This increases the risk of miscarriage and can also cause various complications for the unborn baby.
- Congenital heart disease
- Some changes in facial shape
- Low birth weight
- Small head (microcephaly)
But don't be afraid. If you have PKU, talk to your doctor and follow a special diet throughout your pregnancy, you too can have a completely healthy baby .
Why does PKU develop? What is the cause?
As we discussed earlier, PKU is a genetic disease. It is caused by a mutation in a gene called `PAH` in our body. This `PAH` gene instructs our body to make the enzyme that breaks down phenylalanine. When there is a mutation in the gene, that enzyme is not produced, or there is a defect in its production.
This disease is inherited in an autosomal recessive pattern. Simply put, it goes like this:
For a baby to develop the disease, they must receive one copy of the altered gene from both their mother and father . If they only get the gene from one parent, the baby will not develop the disease. However, that parent may be a carrier. This means that they may not have symptoms, but they can pass the gene on to their children in the future.
How do doctors diagnose PKU?
Identifying PKU has become much easier now thanks to newborn screening.
Between 24 and 72 hours after your baby is born, a doctor or nurse at the hospital will prick your baby's heel with a small needle and collect a few drops of blood on a special card. This is called a 'heel prick test.' This blood sample is used to check the level of phenylalanine in your baby's blood.
If the blood level of phenylalanine is high, further blood and urine tests are done to confirm the diagnosis. Sometimes, a genetic test can be done to identify the specific genetic change that causes the disease.
What are the treatments for PKU?
There is no cure for PKU. However, the condition can be managed very well throughout life . Symptoms may recur if treatment is stopped. The main treatment is a special diet and sometimes medication.
1. A special diet low in phenylalanine
This is the most important and fundamental part of PKU management. A person with PKU must follow a diet low in phenylalanine for the rest of their life.
Since phenylalanine is a part of protein, protein-rich foods need to be limited .
- Meat, fish, chicken
- Eggs
- Milk and dairy products (yogurt, cheese)
- Grains like lentils and chickpeas
- Soy products
- Nuts
However, since the body needs a certain amount of protein for growth, you should talk to a dietitian to determine how much protein you can consume. They will create a nutritious meal plan that is appropriate for the child/person with PKU.
Very important: The artificial sweetener 'aspartame' should be completely avoided. Aspartame is broken down in the body to produce phenylalanine. Many drinks, foods, chewing gums, some vitamins, and cough syrups labeled 'diet' or 'sugar-free' may contain it. Therefore, it is very important to read the label carefully before eating or drinking anything.
Newborn babies with PKU should be started on a special formula that does not contain phenylalanine immediately.
2. Medications
For some PKU patients, medications may be helpful in addition to diet. These should only be used on the recommendation of a doctor.
- Sapropterin dihydrochloride (Kuvan®): This medication helps some patients break down phenylalanine in the body. However, you should continue to follow a diet while taking this medication.
- Pegvaliase (Palynziq®): This is a vaccine recommended for adult patients. It provides the body with an enzyme that breaks down phenylalanine.
Is it possible to live a normal life with PKU?
Yes, it definitely is! Although PKU is a lifelong condition, if detected early and managed properly, its impact on health can be minimized.
Following a low-protein diet for the rest of your life can be challenging at times. But you are not alone. Your doctor and nutritionist are always there to help you. Also, joining support groups with other people with PKU can help you share experiences and gain strength.
You may have seen some 'diet' drink bottles and chewing gum packets with a warning saying "Phenylketonurics: Contains phenylalanine." This is to inform people with PKU that the product contains aspartame, which contains phenylalanine.
If you or your family are feeling stressed about your PKU condition, don't hesitate to talk to a mental health counselor . Mental health is just as important as physical health.
Take-Home Message
- PKU is a treatable and controllable genetic disease. Don't be unnecessarily afraid of it.
- Early detection of the disease through newborn screening is the key to successful treatment.
- The main treatment is to follow a special diet low in phenylalanine for life.
- When purchasing foods and drinks labeled 'Diet' or 'Sugar-free', always check to see if they contain aspartame.
- Follow the instructions given by your doctor and nutritionist exactly. Stay in touch with them regularly.
- With proper management, a child or person with PKU can live a completely healthy, normal, and happy life.
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