Phenylketonuria

What is Phenylketonuria?

What are some common symptoms?

How is Phenylketonuria inherited?

Who is affected by Phenylketonuria?

Are there any available treatments?

For more information...

What is Phenylketonuria?

Phenylketonuria (PKU) is a rare, inherited metabolic disorder in which the enzyme phenylalanine hydroxylase (an enzyme that normally breaks down the amino acid phenylalanine into another amino acid tyrosine) is defective because of a single gene mutation. The result is an accumulation of the amino acid phenylalanine in the body, which in large amounts is very toxic, concentrating in the central nervous system, leading to mental retardation and other severe nervous system impairments and eventually can even lead to death. However, if the person is treated in the first weeks of life and put on a restricted diet that excludes any foods containing phenylalanine, then the disease can be controlled and the person can lead an otherwise normal life.

What are some common symptoms?

Though the main symptom of PKU in untreated patients is mental retardation caused by the build-up of the amino acid phenylalanine, some other symptoms can include 'mousy' odor; light pigmentation; peculiarities of gait, stance, and sitting posture; eczema (a skin disorder); and epilepsy. There is even some suggestion that people who are diagnosed with PKU are slightly shorter in height and have a smaller head circumference than average people of the normal population.

Also, if treatment is discontinued, problems such as drops in IQ and learning disabilities result. Also, behavior problems such as hyperactivity and irritability, neurological problems such as tremors, and personality disorders including schizophrenia, panic attacks and agoraphobia (anxiety of being in a place where escape may be difficult or embarrassing, such as standing in a crowd, or being on a bus) can result.

How is Phenylketonuria inherited?

Phenylketonuria is an autosomal recessive disease meaning that in order to show the phenotype (outward characteristics of the disease) both alleles of PKU must be present in the person. Autosomal recessive diseases often skip a generation, and because PKU is rare, it may not show up in the family line until several generations later. PKU is caused by a mutation of the gene at 12q24.1 that makes the enzyme phenylalanine hydroxylase inactive. With each pregnancy in which both parents are carriers of the disease, there is 1 in 4 (25%) chance of their children becoming affected by the disease.

Who is affected by Phenylketonuria?

PKU affects approximately 1 in 10,000 babies born in the United States and several hundreds of babies born are put on the special restricted diet every year. Because PKU is an autosomal disease, both males and females are equally likely to be affected. PKU is not more common among any specific ethnic group or race.

Are there any available treatments?

The best way to treat PKU is to detect it early on in infancy and put the newborn on a restricted diet that keeps phenylalanine levels down in the body and allows for normal development of the nervous system. The restricted diet includes excluding all food that is high in protein (which would contain phenylalanine) since proteins are made up of amino acids, such as cheese, eggs, ice cream, red meat, poultry, fish, beans. In addition to food products, people who have PKU must also be wary of any other products that contain phenylalanine. For example, several over-the-counter drugs have phenylalanine in them, such as Dimetapp, Tylenol, and Pediacare.

Doctors once believed that after the brain has substantially developed, a person affected with PKU could be taken off the diet; however, it is now known that if a person is taken off the special diet, it can cause several problems such as those described in the symptoms portion above. Therefore it is now believed that the best treatment for the patient is to have the patient follow the diet throughout his/her entire lifetime.

This target is an easy way to visualize the foods allowed on the diet for PKU. Phenyl-Free* is the center of the target diet. As the foods get further away from the bull's-eye, they are higher in phenylalanine. The foods outside the target are not included in the low-phenylalanine meal plan.

For more information...

National PKU News
http://www.pkunews.org

Technical Description of PKU
http://www3.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?261600

Photo courtesy of http://depts.washington.edu/pku/diet.html

	Phenylketonuria

	What is Phenylketonuria? What are some common symptoms? How is Phenylketonuria inherited? Who is affected by Phenylketonuria? Are there any available treatments? For more information... What is Phenylketonuria? Phenylketonuria (PKU) is a rare, inherited metabolic disorder in which the enzyme phenylalanine hydroxylase (an enzyme that normally breaks down the amino acid phenylalanine into another amino acid tyrosine) is defective because of a single gene mutation. The result is an accumulation of the amino acid phenylalanine in the body, which in large amounts is very toxic, concentrating in the central nervous system, leading to mental retardation and other severe nervous system impairments and eventually can even lead to death. However, if the person is treated in the first weeks of life and put on a restricted diet that excludes any foods containing phenylalanine, then the disease can be controlled and the person can lead an otherwise normal life. What are some common symptoms? Though the main symptom of PKU in untreated patients is mental retardation caused by the build-up of the amino acid phenylalanine, some other symptoms can include 'mousy' odor; light pigmentation; peculiarities of gait, stance, and sitting posture; eczema (a skin disorder); and epilepsy. There is even some suggestion that people who are diagnosed with PKU are slightly shorter in height and have a smaller head circumference than average people of the normal population. Also, if treatment is discontinued, problems such as drops in IQ and learning disabilities result. Also, behavior problems such as hyperactivity and irritability, neurological problems such as tremors, and personality disorders including schizophrenia, panic attacks and agoraphobia (anxiety of being in a place where escape may be difficult or embarrassing, such as standing in a crowd, or being on a bus) can result. How is Phenylketonuria inherited? Phenylketonuria is an autosomal recessive disease meaning that in order to show the phenotype (outward characteristics of the disease) both alleles of PKU must be present in the person. Autosomal recessive diseases often skip a generation, and because PKU is rare, it may not show up in the family line until several generations later. PKU is caused by a mutation of the gene at 12q24.1 that makes the enzyme phenylalanine hydroxylase inactive. With each pregnancy in which both parents are carriers of the disease, there is 1 in 4 (25%) chance of their children becoming affected by the disease. Who is affected by Phenylketonuria? PKU affects approximately 1 in 10,000 babies born in the United States and several hundreds of babies born are put on the special restricted diet every year. Because PKU is an autosomal disease, both males and females are equally likely to be affected. PKU is not more common among any specific ethnic group or race. Are there any available treatments? The best way to treat PKU is to detect it early on in infancy and put the newborn on a restricted diet that keeps phenylalanine levels down in the body and allows for normal development of the nervous system. The restricted diet includes excluding all food that is high in protein (which would contain phenylalanine) since proteins are made up of amino acids, such as cheese, eggs, ice cream, red meat, poultry, fish, beans. In addition to food products, people who have PKU must also be wary of any other products that contain phenylalanine. For example, several over-the-counter drugs have phenylalanine in them, such as Dimetapp, Tylenol, and Pediacare. Doctors once believed that after the brain has substantially developed, a person affected with PKU could be taken off the diet; however, it is now known that if a person is taken off the special diet, it can cause several problems such as those described in the symptoms portion above. Therefore it is now believed that the best treatment for the patient is to have the patient follow the diet throughout his/her entire lifetime. This target is an easy way to visualize the foods allowed on the diet for PKU. Phenyl-Free* is the center of the target diet. As the foods get further away from the bull's-eye, they are higher in phenylalanine. The foods outside the target are not included in the low-phenylalanine meal plan. For more information... National PKU News http://www.pkunews.org Technical Description of PKU http://www3.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?261600 Photo courtesy of http://depts.washington.edu/pku/diet.html