Overview

Phenylketonuria (fen-ul-key-toe-NU-ree-uh), also called PKU, is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body. PKU is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine.

Without the enzyme necessary to process phenylalanine, a dangerous buildup can develop when a person with PKU eats foods that contain protein or eats aspartame, an artificial sweetener. This can eventually lead to serious health problems.

For the rest of their lives, people with PKU — babies, children and adults — need to follow a diet that limits phenylalanine, which is found mostly in foods that contain protein.

Babies in the United States and many other countries are screened for PKU soon after birth. Recognizing PKU right away can help prevent major health problems.

Source: http://www.mayoclinic.com

Symptoms

Newborns with PKU initially don't have any symptoms. However, without treatment, babies usually develop signs of PKU within a few months.

PKU signs and symptoms can be mild or severe and may include:

• A musty odor in the breath, skin or urine, caused by too much phenylalanine in the body
• Neurological problems that may include seizures
• Skin rashes (eczema)
• Fair skin and blue eyes, because phenylalanine can't transform into melanin — the pigment responsible for hair and skin tone
• Abnormally small head (microcephaly)
• Hyperactivity
• Intellectual disability
• Delayed development
• Behavioral, emotional and social problems
• Psychiatric disorders

Severity varies

The severity of PKU depends on the type.

• Classic PKU. The most severe form of the disorder is called classic PKU. The enzyme needed to convert phenylalanine is missing or severely reduced, resulting in high levels of phenylalanine and severe brain damage.
• Less severe forms of PKU. In mild or moderate forms, the enzyme retains some function, so phenylalanine levels are not as high, resulting in a smaller risk of significant brain damage.

But most children with the disorder still require a special PKU diet to prevent intellectual disability and other complications.

Pregnancy and PKU

Women who have PKU and become pregnant are at risk of another form of the condition called maternal PKU. If women don't follow the special PKU diet before and during pregnancy, blood phenylalanine levels can become high and harm the developing fetus or cause a miscarriage.

Even women with less severe forms of PKU may place their unborn children at risk by not following the PKU diet.

Babies born to mothers with high phenylalanine levels don't often inherit PKU. But they can have serious consequences if the level of phenylalanine is high in the mother's blood during pregnancy. Complications at birth may include:

• Low birth weight
• Delayed development
• Facial abnormalities
• Abnormally small head
• Heart defects and other heart problems
• Intellectual disability
• Behavioral problems

When to see a doctor

Seek medical advice in these situations:

• Newborns. If routine newborn screening tests show that your baby may have PKU, your child's doctor will want to start dietary treatment right away to prevent long-term problems.
• Women of childbearing years. It's especially important for women with a history of PKU to see a doctor and maintain the PKU diet before becoming pregnant and during pregnancy to reduce the risk of high blood phenylalanine levels harming their unborn babies.
• Adults. People with PKU continue to receive care across the life span. Adults with PKU who have stopped the PKU diet in their teens may benefit from a visit with their doctors. Returning to the diet may improve mental functioning and behavior and slow damage to the central nervous system that can result from high phenylalanine levels.

Source: http://www.mayoclinic.com

Causes

A defective gene (genetic mutation) causes PKU, which can be mild, moderate or severe. In a person with PKU, this defective gene causes a lack of or deficiency of the enzyme that's needed to process phenylalanine, an amino acid.

A dangerous buildup of phenylalanine can develop when a person with PKU eats protein-rich foods, such as milk, cheese, nuts or meat, and even grains such as bread and pasta, or eats aspartame, an artificial sweetener. This buildup of phenylalanine results in damage to nerve cells in the brain.

Inheritance

For a child to inherit PKU, both the mother and father must have and pass on the defective gene. This pattern of inheritance is called autosomal recessive.

It's possible for a parent to be a carrier — to have the defective gene that causes PKU, but not have the disease. If only one parent has the defective gene, there's no risk of passing PKU to a child, but it's possible for the child to be a carrier.

Most often, PKU is passed to children by two parents who are carriers of the disorder, but don't know it.

Source: http://www.mayoclinic.com

Diagnosis

Newborn blood testing identifies almost all cases of phenylketonuria. All 50 states in the United States require newborns to be screened for PKU. Many other countries also routinely screen infants for PKU.

If you have PKU or a family history of it, your doctor may recommend screening tests before pregnancy or birth. It's possible to identify PKU carriers through a blood test.

Testing your baby after birth

A PKU test is done a day or two after your baby's birth. The test is done after your baby is 24 hours old and after your baby has ingested some protein in the diet to ensure accurate results.

• A nurse or lab technician collects a few drops of blood from your baby's heel or the bend in your baby's arm.
• A laboratory tests the blood sample for certain metabolic disorders, including PKU.
• If you don't deliver your baby in a hospital or are discharged soon after the birth, you may need to schedule a newborn screening with your pediatrician or family doctor.

If this test indicates your baby may have PKU:

• Your baby may have additional tests to confirm the diagnosis, including more blood tests and urine tests
• You and your baby may have genetic testing to identify gene mutations

Source: http://www.mayoclinic.com

Complications

Untreated PKU can lead to complications in infants, children and adults with the disorder. When mothers with PKU have high blood phenylalanine levels during pregnancy, fetal birth defects or miscarriage can occur.

Untreated PKU can lead to:

• Irreversible brain damage and marked intellectual disability beginning within the first few months of life
• Neurological problems such as seizures and tremors
• Behavioral, emotional and social problems in older children and adults
• Major health and developmental problems

Source: http://www.mayoclinic.com

Prevention

If you have PKU and are considering getting pregnant:

• Follow a low-phenylalanine diet. Women with PKU can prevent birth defects by sticking to or returning to a low-phenylalanine diet before becoming pregnant. If you have PKU, talk to your doctor before you start trying to conceive.
• Consider genetic counseling. If you have PKU, a close relative with PKU or a child with PKU, you may also benefit from genetic counseling before becoming pregnant. A doctor who specializes in medical genetics (geneticist) can help you better understand how PKU is passed through your family tree. He or she can also help determine your risk of having a child with PKU and assist with family planning.

Lifestyle and home remedies

Some strategies to help manage PKU may include the following.

Keep track and measure correctly

If you or your child is following a low-phenylalanine diet, you'll need to keep records of the food eaten every day to be sure you're sticking to the specific, individualized dietary guidelines recommended by your dietitian.

To be as accurate as possible, measure food portions using standard measuring cups and spoons and a kitchen scale that reads in grams. The food amounts are compared with a food list or are used to calculate the amount of phenylalanine eaten every day. Each meal and snack includes the appropriately divided portion of your daily PKU formula.

Food diaries or computer programs are available that list the amount of phenylalanine in baby foods, solid foods, PKU formulas, and common baking and cooking ingredients.

Buy low-protein products

To add variety to your diet, buy some of the many low-protein products, such as low-protein pasta, rice, flour and bread, which are available through specialty food retailers.

These products allow people with PKU to eat some meals that more closely resemble what everyone else is eating. Like the PKU formulas, these products can be expensive, but you might consider splurging on a few favorites with the money you save on dairy and meat products.

Be creative

Talk with your dietitian to find out how you can be creative with foods to help you stay on track. For example, use seasonings and a variety of cooking methods to transform lower phenylalanine vegetables into a whole menu of different dishes. Herbs and flavorings low in phenylalanine can pack a flavorful punch. Just remember to measure and count every ingredient and adjust recipes to your individualized diet.

If you have any other health conditions, you may also need to consider those when you plan your diet. Talk with your doctor or dietitian if you have any questions.

Source: http://www.mayoclinic.com

Coping and support

Living with PKU can be challenging. These strategies may help:

• Stay informed. Knowing the facts about PKU can help you take charge of the situation. Discuss any questions with your pediatrician, family doctor, geneticist or dietitian. Read books and cookbooks specifically written for people with PKU.
• Learn from other families. Ask your doctor about local or online support groups for people dealing with PKU. Talking with others who have mastered similar challenges can be very helpful. The National PKU Alliance is an online support group for adults with PKU.
• Get help with menu planning. A registered dietitian with experience in PKU can help you devise delicious low-phenylalanine dinners. He or she may also have great ideas for holiday meals and birthdays.
• Plan ahead when you eat out. A meal at the local restaurant gives you a break from the kitchen and can be fun for the whole family. Most places offer something that fits into the PKU diet. But you may want to call ahead and ask about the menu or bring food from home.
• Find sources of financial aid. Ask your doctor or dietitian if there are programs or insurance plans that help cover the high costs of formula and low-protein foods. Also, see if your local school lunch program will accommodate special dietary needs.
• Don't focus on food. Encourage children with PKU to focus on sports, music or favorite hobbies, not on just what they can and can't eat. Also consider creating holiday traditions that center on special projects and activities, not just food.
• Let your child help manage his or her diet as early as possible. Toddlers can make choices about which cereal, fruit or vegetable they'd like to eat and help measure out portions. They can also help themselves to pre-measured snacks. Older children can help with menu planning, pack their own lunches and keep their own food records.
• Make your grocery list and meals with the whole family in mind. A cupboard full of restricted foods can be tempting to a child or adult with PKU, so try to focus on foods that everyone can eat. Serve stir-fried vegetables that are lower in protein. If the other family members wish, they can add peas, corn, meat and rice. Or set up a salad bar with low-protein and moderate-protein options. You can also serve the whole family a delicious low-phenylalanine soup or curry.
• Be prepared for potlucks, picnics and car trips. Plan ahead, so there's always a PKU-friendly food option. Pack dehydrated fruit snacks, raisins and lower protein crackers for the car. Take fruit kebabs or vegetable skewers to a cookout, and make a low-phenylalanine salad for the neighborhood potluck. Other parents, friends and family members will likely be accommodating and helpful if you explain the dietary restrictions.
• Talk to teachers and other staff in your child's school. Your child's teachers and cafeteria staff can be a big help with the PKU diet if you take the time to explain its importance and how it works. By working with your child's teachers, you can also plan ahead for special school events and parties so that your child always has a treat to eat.
• Maintain a positive food attitude. When children know nothing but the foods they are given, they can be surprisingly accepting of the PKU diet — especially when their parents are positive problem-solvers.

Source: http://www.mayoclinic.com

Risk factors

Risk factors for inheriting PKU include:

• Having both parents with a defective gene that causes PKU. Two parents must pass along a copy of the defective gene for their child to develop the condition.
• Being of certain ethnic descent. The gene defect that causes PKU varies by ethnic groups and it's less common in African-Americans than in other ethnic groups.

Source: http://www.mayoclinic.com