What is PKU?
PKU is short for phenylketonuria (pronounced fen’-il-kee’-to-nu’-ria). PKU is a rare, inherited metabolic disease that results in developmental disability and other neurological problems when treatment is not started within the first two weeks of life.
How is PKU diagnosed?
Every baby born in Canada is supposed to be tested for signs of elevated phenylalanine. This effects about one baby in 12,000 in Canada. The reason for this universal newborn screening for PKU is that a baby with PKU does not show signs or symptoms until after irreversible harm has occurred. The lack of early signs and symptoms means the best mother and father working with the best doctors and nurses do not have a good chance of preventing permanent brain damage. That why we call newborn screening a modern miracle.
Most Canadian babies have been screened for PKU since the 1960s. We do not screen children born in other countries when their families move to Canada.
How often are children with PKU born?
PKU is inherited as an autosomal recessive trait. In other words, two people who conceive a child must both be carriers of the gene in order for there to be a chance that their infant will have PKU. When two carriers conceive a child, there is a one in four or 25% chance for each pregnancy that the baby will have PKU.
It is estimated that PKU occurs with a frequency of one in 12,000 newborns in North America. This amounts for about 300 new cases each year. The incidence varies in other parts of the world, it occurs with a frequency of 1 in 4,500 new born babies in Ireland and Turkey, 1 in 10,000 in most of Europe, and 1 in 11,000 in South America.
How can PKU affect a person?
People with PKU are missing an enzyme to break down protein in food, specifically one aminio acid. This amino acid is called phenylalanine, often called PHE (pronounced fee). Since this amino acid cannot be completely processed, it builds up in the blood and excess amounts cross the blood-brain barrier. When excess amounts build up, brain damage and other neurological problems result.
Is it possible to prevent the symptoms?
YES, fortunately, if the child is diagnosed early (before 10 days of age) and treatment is started right away, developmental disability can be prevented. There is a screening program for PKU available for Canadian children, which takes place shortly after birth (newborn screening). All children with PKU have access to treatment. To maintain proper health and development the blood PHE level must be kept in good control throughout the child’s life.
How is PKU treated?
Reduce phenylalanine intake through low PHE diet
Provide necessary alternative to natural protein through œmedical formula
Periodic monitoring of blood PHE levels
Most children and adults with PKU must follow a special food therapy. The therapy often referred to as a "PKU diet" involves strictly controlling the intake of natural protein (which contains phenylalanine), drinking a synthetic phenylalanine-free protein formula and eating special low-protein food. The synthetic formula and special low-protein foods are expensive, but mostly covered here in Canada.
The diet for the most severe form of PKU eliminates all of the very high protein foods since all protein contains phenylalanine. This means that all concentrated sources of protein must be eliminated from the diet in order to limit the amount of phenylalanine. The diet does not allow consumption of meat, fish, poultry, milk, eggs, cheese, ice cream, legumes, nuts, or many products containing regular flour.
A synthetic formula is used as a nutritional substitute for the eliminated foods. This formula is very expensive.
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