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Phenylketonuria In Children


  • Phenylketonuria (fen-il-ke-to-NU-re-ah) is also called PKU. This is an inherited condition where the body cannot break down certain foods properly. With PKU, there is an error with the enzyme that is needed to break down phenylalanine. This enzyme may be present only in small amounts or none at all. Phenylalanine may build up in the body and cause brain damage. Without treatment, signs and symptoms of PKU may appear within a few months. These can be mild or severe and may include problems with learning, speech, or behavior. Other symptoms include vomiting (throwing up), seizures (convulsions), rash, or a musty odor to the breath, hair, or urine.
  • A newborn screening test is usually done a day or two after your baby's birth. His blood is checked for PKU and other genetic disorders. Urine tests, computerized tomography (CT) scan, or magnetic resonance imaging (MRI) may also help diagnose PKU. A special diet is needed to help keep his phenylalanine levels low. Medicines and special formulas may also be given to control your child's symptoms and help with his nutrition. Many children who follow a strict PKU diet grow up to be normal, healthy adults. With treatment, such as medicines and proper diet, your child may grow normally and serious health problems may be prevented.


You have the right to help plan your child's care. Learn about your child's health condition and how it may be treated. Discuss treatment options with your child's caregivers to decide what care you want for your child.


Phenylketonuria may be hard for you and your child. He may have a hard time sticking to his special diet and frequent blood tests. Your child may not be able to eat and enjoy foods and drinks as other children do. Special formulas or products may also be expensive. If PKU is not treated, your child may have permanent brain damage. He may have trouble learning, speaking, paying attention, or doing simple things. Your child's health, quality of life, and ability to function may greatly change without treatment. Ask your caregiver if you are worried or have questions about your child's disorder, treatment, or care.


Informed consent

is a legal document that explains the tests, treatments, or procedures that your child may need. Informed consent means you understand what will be done and can make decisions about what you want. You give your permission when you sign the consent form. You can have someone sign this form for you if you are not able to sign it. You have the right to understand your child's medical care in words you know. Before you sign the consent form, understand the risks and benefits of what will be done to your child. Make sure all of your questions are answered.

Emotional support:

Stay with your child for comfort and support as often as possible while he is in the hospital. Ask another family member or someone close to the family to stay with your child when you cannot be there. Bring items from home that will comfort your child, such as a favorite blanket or toy.


  • A caregiver, called a dietitian, may talk to you about your child's feeding and nutrition. Every child has a special diet that is different from the others. This may depend upon your child's phenylalanine levels, age, weight, and other factors. Your child's dietitian plans and adjusts the amount of protein that your child is allowed.
  • You may breastfeed your baby or give him ordinary milk. If your child is old enough, fruits, vegetables, or cereals may be given. Special formulas or products may be added to your child's foods or liquids. These may add extra calories, vitamins, and minerals that he needs. You may talk to your child's caregivers to learn more about his special diet.


is a small tube placed in your child's vein that is used to give him medicine or liquids.


Your child may have one or more of the following:

  • Anticonvulsant medicine: Anticonvulsants are given to control your child's seizures.
  • Anti-itching medicines: Caregivers may give your child these medicines to help keep his skin from itching. Anti-itching medicines may be given in an IV, as a shot, by mouth, or as a skin lotion.
  • Antinausea medicine: This medicine may be given to calm your child's stomach and control vomiting (throwing up).
  • Muscle relaxants: These medicines may help your child's muscles relax. When the muscles are relaxed, your child may move easier and have less pain.

Neurologic signs:

These are also called neuro signs, neuro checks, or neuro status. During a neuro check, caregivers see how your child's pupils react to light. They may check his memory and how easily he wakes up. His hand grasp and balance may also be tested. How your child responds to the neuro checks can tell caregivers if his illness or injury has affected his brain.


Your child may need one or more of the following tests:

  • Blood tests: Your child may need blood tests to give caregivers information about how his body is working. The blood may be taken from your child's arm, hand, finger, foot, heel, or IV.
  • CT scan: This test is also called a CAT scan. An x-ray and computer are used to take pictures of your child's body. Your child may be given dye, also called contrast, before the test. Tell the caregiver if your child is allergic to dye, iodine, or seafood.
  • Genetic tests: Genetic testing may be needed to check your child's genes. This test helps caregivers learn how your child's genes may affect him. This may also help your child's caregivers decide on a treatment plan.
  • Magnetic resonance imaging scan: This test is also called an MRI. During the MRI, pictures are taken of your child's head. An MRI may be used to look at the brain, muscles, joints, bones, or blood vessels. Your child will need to lie still during an MRI. Never enter the MRI room with an oxygen tank, watch, or any other metal objects. This can cause serious injury. Tell your child's caregiver if your child has any metal implants in his body.
  • Urine tests: A sample of your child's urine may be collected and sent to a lab for tests. These tests help diagnose PKU and other disorders your child may have.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Learn more about Phenylketonuria In Children (Inpatient Care)

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