The Effects and Treatment of PKU
Phenylketonuria (PKU) is a birth defect and another of the things that can affect a newborn child. This particular birth defect is inherited and involves mutation in a gene containing instructions for making the enzyme needed to break down the amino acid phenylalanine. Although PKU is rare, it is imperative that it is recognized quickly, to help prevent serious health problems.
PKU is an inherited disorder of body chemistry that, if untreated, causes mental retardation. In the U.S., 1 in 25,000 babies born will have PKU. It is seen in all ethnic groups, but is more prevalent in Northern European and Native American ancestry than African-American, Hispanic and Asian ancestry. Newborns in the U.S. are by law, routinely screened by pricking the heel for a blood sample. This is done at least 24 hours after delivery for accuracy. Because of this, almost all affected newborns are diagnosed and treated early, resulting in normal intelligence. If you do not deliver in the hospital, make arrangements for a visit to a doctor for this test.
To inherit PKU, a child must receive two abnormal PAH genes (that regulate the production of the enzyme), one from each parent. A parent may have only one abnormal gene and not express the disorder, thus the parent is a “carrier” and is not effected in any way. When both parents are carriers, there is a 1-4 (25%) chance the baby will be born with PKU. There is an equal chance both parents will pass on the normal gene, and the baby will not have the disease nor be a carrier. There is a 2-4 (50%) chance the baby will inherit one abnormal and one normal gene, making it a carrier like the parents.
Children born with PKU appear normal for the first few months. If untreated, by 3 to 6 months they begin to lose interest in their surroundings. By the time they are 1 year old, they appear obviously developmentally delayed. Children with untreated PKU often have mental retardation, are irritable and have behavioral problems, are hyperactive, and have microcephaly (small head size). They may have a musty odor, and dry skin, rashes or seizures. They tend to have fair skin and blue eyes, because phenylalanine cannot transform into melanin, the pigment responsible for hair and skin tone
Treatment involves a strict diet to avoid high-protein foods, such as, milk, eggs, cheese, nuts, soybeans, beans, meat, chocolate, peas and limited, pasta, rice, bread, cookies, and certain fruits and vegetables. There is a special formula for “milk” and special foods can also be purchased. Diet drinks and food containing aspartame (NutraSweet, Equal) must be avoided, as they release phenylalanine when digested.
A safe amount of phenylalanine differs for each person. A doctor determines the safe amount, through regular review of diet records, growth charts and blood levels of phenylalanine. Frequent blood tests are used to monitor PKU levels, as they change over time, especially during childhood. With strict attention and monitoring, these children grow up healthy and bright. Doctors once believed the diet could be stopped in adolescence, but now recommend it for life.
