Infants with classic PKU appear normal until they are a few months old. Without treatment, these children develop permanent intellectual disability. Seizures, delayed development, behavioral problems, and psychiatric disorders are also common. Untreated individuals may have a musty or mouse-like odor as a side effect of excess phenylalanine in the body.
Children with classic PKU tend to have lighter skin and hair than unaffected family members and are also likely to have skin disorders such as eczema. Less severe forms of this condition, sometimes called variant PKU and non-PKU hyperphenylalaninemia, have a smaller risk of brain damage. People with very mild cases may not require treatment with a low-phenylalanine diet.
Babies born to mothers who have PKU and uncontrolled phenylalanine levels women who no longer follow a low-phenylalanine diet have a significant risk of intellectual disability because they are exposed to very high levels of phenylalanine before birth. These infants may also have a low birth weight and grow more slowly than other children. Other characteristic medical problems include heart defects or other heart problems, an abnormally small head size microcephaly , and behavioral problems.
Women with PKU and uncontrolled phenylalanine levels also have an increased risk of pregnancy loss. The occurrence of PKU varies among ethnic groups and geographic regions worldwide. Most cases of PKU are detected shortly after birth by newborn screening, and treatment is started promptly. As a result, the severe signs and symptoms of classic PKU are rarely seen.
Mutations in the PAH gene cause phenylketonuria. The PAH gene provides instructions for making an enzyme called phenylalanine hydroxylase. This enzyme converts the amino acid phenylalanine to other important compounds in the body.
If gene mutations reduce the activity of phenylalanine hydroxylase, phenylalanine from the diet is not processed effectively. As a result, this amino acid can build up to toxic levels in the blood and other tissues. Because nerve cells in the brain are particularly sensitive to phenylalanine levels, excessive amounts of this substance can cause brain damage. Phenylalanine is an essential amino acid and it is found in nearly all foods which contain protein: meat of all kinds , dairy products, nuts, beans, tofu Those of us that have PKU must follow a strict "low protein" diet to avoid all food sources that have high phenylalanine content.
To get adequate amounts of other amino acids found in protein without the damaging phenylalanine , people with PKU also have to take a special formula which is usually in the form of a liquid beverage. If those of us that have PKU do not follow a strict low protein diet, phenylalanine is not adequately digested in our bodies and it builds up in our blood in the form of an acid called phenylpyruvic acid. Depending on the severity of the PKU, babies who were not treated for the disorder and put on the special diet at birth run the risk of suffering irreversible mental retardation within the first year of life.
PKU is certainly a detrimental disorder if not treated properly, but the prognosis isn't nearly as grim as the preceding paragraph suggests. If babies are put on the low protein diet at a young age, and they follow the diet throughout life, there is no evidence that their PKU will be a major hindrance in their accomplishments.
In fact, in some cases, myself included people with PKU view their disorder as being a positive trait, one which has taught them to be more self-disciplined. In the past, children were taken off the low protein PKU diet at age 5 or 6 because it was believed that at this age the brain had developed to the point where elevated levels of phenylpyruvic acid in the blood would not cause severe health problems.
These children are now adults; many of them have noticed health problems and have decided, of their own accord, to return to the PKU diet. These days, most doctors that provide care for PKU patients preach that the low protein PKU diet should be a way of life and, if we value our health and well-being, those of us with the disorder should never stray from it.
One question that I often get asked by people who read this webpage - "Is phenylalanine harmful to people that don't have PKU? If phenylalanine is in it's natural form, then the answer to this question is a great big resounding NO. Phenylalanine is an essential amino acid that is in nearly all proteins - meats, dairy products, eggs, nuts, legumes Some researchers claim that the amino acid phenylalanine is a natural muscle relaxer and sleep aid.
For people without PKU or other metabolic disorders, it is very important to eat a balanced diet, and this certainly includes high protein high phenylalanine foods. We are grateful that we can control her disorder with diet and thankful to the folks at Riley for their kindness and expertise. The next time you see the Phenylketonurics: Contains Phenylalanine warning, think of a blond-headed baby girl, not an alien!
The Tri-State's Best Talk. The Mom of a Phenylketonuric Explains. Ash Published: January 13, Share on Facebook Share on Twitter. Categories: What's New.
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