Women who have high levels of phenylalanine during pregnancy are at high risk for having babies born with mental retardation, heart problems, small head size microcephaly and developmental delay.
This is because the babies are exposed to their mother's very high levels of phenylalanine before they are born. Newborn screening has been used to detect PKU since the 's. As a result, the severe signs and symptoms of PKU are rarely seen. Symptoms of PKU range from mild to severe. Infants born with classic PKU appear normal for the first few months after birth. However, without treatment with a low-phenylalanine diet, these infants will develop mental retardation and behavioral problems.
Other common symptoms of untreated classic PKU include seizures, developmental delay, and autism. Boys and girls who have classic PKU may also have eczema of the skin and lighter skin and hair than their family members who do not have PKU.
Babies born with less severe forms of PKU moderate or mild PKU may have a milder degree of mental retardation unless treated with the special diet. If the baby has only a very slight degree of PKU, often called mild hyperphenylalaninemia, there may be no problems and the special dietary treatment may not be needed.
PKU is usually diagnosed through newborn screening testing that is done shortly after birth on a blood sample heel stick. Phenylalanine is a building block of proteins an amino acid that is obtained through the diet. It is found in all proteins and in some artificial sweeteners. If PKU is not treated, phenylalanine can build up to harmful levels in the body, causing intellectual disability and other serious health problems.
The signs and symptoms of PKU vary from mild to severe. The most severe form of this disorder is known as classic PKU. 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. Subscribe for free and receive your in-depth guide to digestive health, plus the latest on health innovations and news.
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To have an autosomal recessive disorder, you inherit two mutated genes, one from each parent. These disorders are usually passed on by two carriers. Their health is rarely affected, but they have one mutated gene recessive gene and one normal gene dominant gene for the condition. 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. 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. Untreated PKU can lead to complications in infants, children and adults with the disorder.
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