CHILDREN'S HEALTH Birth Defects • Down syndrome • Fetal alcohol syndrome • Phenylketonuria • Ambiguous genitalia • Rett syndrome • Cleft lip and cleft palate • Familial Mediterranean fever • Clubfoot

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A quick needle stick to the heel, and a moment of anxiety for the parents, gives many newborns a prickly welcome to the world as part of the screening process for phenylketonuria (fen-ul-ke-to-NU-re-uh). Through the few drops of blood collected from the heel prick, the test for phenylketonuria (PKU ) can quickly detect — or rule out — this rare birth defect. Undetected phenylketonuria can cause long-term problems such as mental retardation.

Phenylketonuria is a type of birth defect a child inherits from both parents, who pass along the abnormal gene. A person who has phenylketonuria is missing or deficient in a specific enzyme needed to process an essential amino acid called phenylalanine. Amino acids are the building blocks for protein. For babies or adults with phenylketonuria, too much of this amino acid can be dangerous. An affected newborn needs special low-phenylalanine formula to meet its nutritional needs. Older children and adults must continue to follow a strict diet low in this amino acid.

Although phenylketonuria is rare, recognizing it right away can help prevent serious health problems.

Newborns who have phenylketonuria don't have any symptoms. Without treatment, though, babies usually develop signs of PKU within a few months. Signs and symptoms can be mild or severe and may include:

• Mental retardation
• Behavioral or social problems
• Seizures, tremors or jerking movements in the arms and legs
• Rocking
• Hyperactivity
• Stunted growth
• Skin rashes (eczema)
• Small head size (microcephaly)
• Vomiting
• A musty odor in the child's breath, skin or urine, caused by too much phenylalanine in the body
• Fair skin and blue eyes, because phenylalanine cannot transform into melanin — the pigment responsible for hair and skin tone

The most severe form of the disorder is known as classic PKU. Children with untreated classic PKU usually develop obvious, permanent mental retardation and behavioral problems by their first birthdays. However, even in people with exactly the same genetic defect, the severity of the disease may be different.

Less severe forms of PKU — sometimes called mild or moderate PKU — have a smaller risk of significant brain damage, but most children with these forms of the disorder still require a special diet to prevent mental retardation and other complications.

Pregnancy and PKU
A woman who has PKU and becomes pregnant is at risk of another form of the condition called maternal PKU. Many people with PKU used to stop following a low-phenylalanine diet during their teen years, as was directed by doctors at the time. But, doctors now know that if a woman doesn't follow the diet during pregnancy, blood phenylalanine levels can become very high and harm the developing fetus. Because of this, and other reasons, doctors recommend that anyone with PKU follow the low-phenylalanine diet for life.

Although babies born to mothers with high phenylalanine levels may have complications at birth, most don't actually inherit PKU and won't need to follow a PKU diet after birth. However, these babies are at risk of being born with mental retardation or an abnormally small head (microcephaly). They may also have heart defects, low birth weights and behavioral problems.

A mutation in a single gene causes PKU. This gene contains the instructions for making an enzyme needed to process the amino acid called phenylalanine. Amino acids are the building blocks for protein. In a person with PKU, this gene is defective, causing a complete or near-complete deficiency of the enzyme. Without the enzyme necessary to process phenylalanine, a dangerous buildup of this amino acid can develop when a person with PKU eats foods that are high in protein, such as milk, cheese, nuts or meats. This can eventually lead to serious health problems.

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. A parent can have the defective gene, but not have the disease. This is called being a "carrier." Most often, PKU is passed down the family tree by parents who are carriers of the disorder but don't know it.

A child's genetic makeup holds the possibility of inheriting PKU. Both parents must pass along a copy of the mutated PKU gene for their child to develop this condition. If only one parent has the PKU gene, there's no risk of passing PKU to a child. The gene defect occurs mainly in white people of Northern European ancestry. It's much less common in black or Asian people.

Children of mothers who have PKU but who didn't follow the PKU diet during pregnancy also may be affected. Although these children don't often have PKU, they do have consequences of the high level of phenylalanine in the mother's blood.

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. Newborns with PKU are started on a special formula. Your doctor may refer you to a specialist in genetics and a dietitian or nutritionist who can help you learn about the PKU diet.
• Adults. Older adults with PKU who stopped the PKU diet in their teens may also benefit from a trip to the doctor. Although adolescents with PKU were allowed to go "off-diet" in the past, doctors now recommend that anyone with PKU continue the special diet for life. Returning to the diet can improve mental functioning and behavior and slow damage to the central nervous system in adults with high phenylalanine levels.
• Women. It's especially important for women with a history of PKU to see a doctor and return to the PKU diet before becoming pregnant. Even mild cases of maternal PKU can pose a risk to unborn babies. Pregnant women with PKU who aren't on the special diet also have a higher risk of miscarriage.

Newborn screening identifies almost all cases of PKU. All 50 states in the United States require newborns to be tested for PKU. Canada and many other countries also routinely screen infants for PKU.

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

A PKU test is conducted a day or two after your baby's birth. In the test, a nurse or lab technician collects a few drops of blood from your baby's heel or the crook of your baby's arm using a needle or lancet. A laboratory tests the blood sample for certain metabolic disorders, including PKU. Tests for PKU are highly accurate when done between 24 hours and seven days after birth and are typically done before a new baby leaves the hospital. The test is not done before the baby is 24 hours old or before the baby has ingested some protein in the diet. 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 your baby's blood sample shows a high level of phenylalanine, he or she will need to be fed a special formula. Your doctor can help you find the right type of formula to feed your baby.

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

It's also possible to detect PKU in a developing fetus using chorionic villus sampling (CVS). During this procedure, a needle is inserted through a pregnant woman's lower belly. Another option is to insert a catheter up through the cervix into the chorionic villi, which forms the lining of the placenta. Through the needle, your doctor removes a small sample of cells for genetic testing. Your doctor and a genetics counselor can help you decide if these tests are right for you and what to do with the results.

Untreated PKU leads to irreversible brain damage and marked mental retardation within the first few months of life. Older children with untreated PKU may also develop behavioral problems and seizures. Damage to the central nervous system may cause a child with PKU to become irritable, restless and destructive.

Newborn screening and treatment for affected babies helps prevent these complications.

The main treatment for PKU is a strict diet with very limited levels of phenylalanine, which is mostly found in protein. Doctors used to believe it was OK for a person with PKU to stop the diet in adolescence, but today, doctors recommend sticking to the diet for life.

A safe amount of phenylalanine differs for each person. Your doctor will determine a safe amount through regular review of diet records, growth charts and blood levels of phenylalanine. Frequent blood tests will monitor PKU levels as they change over time, especially during childhood growth spurts and pregnancy. In general, the idea is to consume only the amount of phenylalanine that's necessary for normal growth and body processes, but no more.

Because the amount of phenylalanine adults can eat is so low, it's crucial they avoid all high-protein foods, such as milk, ice cream, eggs, nuts, beans, chicken, steak and fish.

Children and adults should also avoid foods, including many diet sodas, and medications made with aspartame (NutraSweet, Equal). Aspartame, found in many artificial sweeteners, releases phenylalanine when digested. Because the amount of phenylalanine allowed in the PKU diet is so small, adults and children will also have to limit pasta, rice, bread, cookies, and even some fruits and vegetables.

For instance, one ear of corn on the cob contains more than 200 milligrams of phenylalanine — which can be nearly half or all of a person's allotment for the day. Too much of a good thing can be harmful. Even if you are eating approved foods, eating too many at one time can be dangerous. Consider the total amount of phenylalanine in all the foods you eat when planning your diet.

Focus on formula
You might wonder how someone, particularly a baby, can get all of the necessary nutrition with these dietary limitations. The answer is a formula — a special nutritional drink or supplement for people with PKU. The formula contains phenylalanine-free protein substitutes and essential nutrients but contains little or no phenylalanine. It provides the needed nutrients in a form that is safe for people with PKU.

Because regular infant formula and breast milk contain phenylalanine, babies with PKU are promptly put on a phenylalanine-free infant formula. Parents introduce solid foods with low levels of phenylalanine to children with PKU on the same schedule used for other infants. A measured amount of breast milk may be OK for some babies. However, a safe amount must be carefully calculated under the direction of your child's doctor.

Older children and adults continue to drink several glasses of formula each day, as directed by a doctor or dietitian. The formula for older kids and adults is not the same as the one used for infants, but it works on the same principle. It acts as a nutritional substitute and is continued for life.

The need for a nutritional supplement and the limited food choices can make the PKU diet challenging. But, it is the only way to prevent the serious health problems people with PKU can develop. Families need to commit to this lifestyle change wholeheartedly, realizing that it may be difficult but not impossible.

Applying the PKU diet
If you or your child is "on-diet," you'll need to keep records of the amount of phenylalanine eaten every day to be sure you're sticking to the specific, individualized dietary guidelines recommended by your dietitian. To do so, use a food diary or computer program that lists the amount of phenylalanine in baby foods, solid foods, PKU formulas, and common baking and cooking ingredients. To be as accurate as possible, measure portions, using standard measuring cups and spoons and a kitchen scale that reads in grams.

Investing in some of the many low-protein products available through specialty food retailers may add variety to your diet. You'll find low-protein rice, pasta, pizza crusts, tortillas, bagels, breads, cookie dough and baking mixes, as well as egg substitutes and imitation cheeses. These products provide some dietary variety, and they allow people with PKU to eat lunches and dinners 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.

Whether you buy special low-protein products or not, you can be creative with foods you can find at your local grocery store. Here are some ideas for serving up three square meals with low amounts of phenylalanine:

• Breakfast. In the morning, dish up lower phenylalanine cereals, such as corn flakes or puffed rice, swimming in nondairy creamer diluted with water. Or whip up a smoothie by blending fresh or frozen fruit with ice cubes, fruit juice, and almond or vanilla flavoring.
• Lunch. Pack a lunch bag with small portions of rice cakes, grapes, applesauce, lemonade and jelly beans. Or slurp up a low-protein pumpkin or vegetable soup.
• Dinner. Veggie stir-fry and a salad makes a great evening meal. So do vegetable shish kebabs, soaked in a tangy vinaigrette or Asian marinade. You can also try eggplant curry, baked potatoes topped with broccoli or mushrooms, and peppers stuffed with sweet potatoes or carrots.

You can transform the same basic lower phenylalanine vegetables into a whole menu of different dishes, using a little creativity — and a lot of seasonings. Herbs and flavorings such as basil, cilantro, lemon juice, soy sauce, sesame oil, maple syrup and honey are low in phenylalanine, but they pack a flavorful punch. Just remember to measure and count every ingredient and adjust ideas to your individualized diet. Talk to your doctor or dietitian if you have any questions. If you have any other health conditions, you may need to consider those when you plan your diet too.

Women with PKU can prevent birth defects by sticking to — or returning to — a low-phenylalanine diet before becoming pregnant. Even women with mild PKU may place their unborn children at risk by not following the special PKU diet. If you're a woman with a history of PKU, talk to your doctor before you start trying to conceive.

If you have a history of PKU, a close relative with PKU or a child with PKU, you may also benefit from preconception genetic counseling. A doctor who specializes in medical genetics can help you better understand how PKU is passed through your family tree. He or she can also help you determine your risk of having a child with PKU and assist with family planning.

Living with PKU can be difficult. The combination of a limited diet, expensive groceries, regular blood tests, detailed food records and frequent visits to the doctor can make for trying and frustrating times. The following strategies may help:

• Be informed. Knowing the facts about PKU can help you take better charge of the situation. Discuss any questions with your pediatrician, family doctor or a doctor who specializes in medical genetics. And read books and cookbooks specifically written for people with PKU, such as "Low Protein Cookery for PKU" by Virginia Schuett.
• Learn from other families. Ask your doctor how you can link up with other parents who have successfully managed their child's PKU. Talking with others who have mastered similar challenges can be very helpful.
• Get help with menu planning. A registered dietitian or nutritionist 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.
• Try to eat out. A meal at the local cafe or neighborhood pizzeria 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, even if it's just french fries and salad. But you may want to call ahead and ask about the menu or bring food from home. Some restaurants will even agree to heat up a low-protein product, if you make arrangements in advance.
• Find sources of financial aid. Ask your doctor or dietitian if there are programs or insurance companies in your area 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.

If you have a child with PKU, it can be difficult to explain why he or she can't eat "normal" foods. Worse yet, mealtimes and snack times can be a battle. Here are some tips for avoiding food fights and creating a better buffet:

• Don't focus on food. Encourage children with PKU to focus on sports, music and favorite hobbies, not just what they can and can't eat. Also consider creating holiday traditions that center on special projects and activities, not just food. At your house, Thanksgiving can revolve around making a crafty cornucopia, not just eating turkey.
• Let your child 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 your meals with the whole family in mind. A cupboard full of restricted foods can be tempting and irritating to a child or adult with PKU, so try to limit the number of forbidden foodstuffs. Also try to avoid making separate meals that single out a child with PKU. Instead, make one meal for the whole family, even if the PKU child can't eat everything. Serve stir-fried vegetables with meat, cashews and rice on the side, or set up a salad bar with low-protein and high-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 fruit roll-ups, raisins and crackers for the car. Take fruit shish 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.
• Be sure your child's school is schooled in the PKU diet. 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 your child always has a treat to eat.
• Maintain a positive food attitude. When children know nothing but the foods they are given, they are surprisingly accepting of the PKU diet — especially when their parents are positive problem solvers.