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Which are the causes of Phenylketonuria?

See some of the causes of Phenylketonuria according to people who have experience in Phenylketonuria

Phenylketonuria causes

Phenylketonuria (PKU) is a rare genetic disorder that affects the body's ability to process an essential amino acid called phenylalanine. This condition is caused by a mutation in the gene responsible for producing an enzyme called phenylalanine hydroxylase (PAH). Without this enzyme, phenylalanine builds up to toxic levels in the blood and brain, leading to various health problems.



Genetic Mutation: The primary cause of PKU is a genetic mutation in the PAH gene. This gene provides instructions for making the PAH enzyme, which is responsible for converting phenylalanine into another amino acid called tyrosine. In individuals with PKU, the mutation impairs the production or function of the PAH enzyme, resulting in the accumulation of phenylalanine.



Autosomal Recessive Inheritance: PKU follows an autosomal recessive pattern of inheritance. This means that both parents must carry a copy of the mutated gene for their child to be affected. If both parents are carriers, there is a 25% chance with each pregnancy that their child will have PKU. If only one parent is a carrier, the child will be a carrier but not affected by the disorder.



Phenylalanine-Restricted Diet: Another important factor contributing to the development of PKU is the dietary intake of phenylalanine. Individuals with PKU lack the ability to break down phenylalanine effectively, leading to its accumulation in the body. Therefore, a phenylalanine-restricted diet is crucial in managing PKU. This diet involves avoiding high-protein foods, such as meat, fish, eggs, dairy products, nuts, and certain grains, as they are rich in phenylalanine. Instead, individuals with PKU consume specially formulated low-protein foods and medical supplements to meet their nutritional needs.



Untreated PKU: If left untreated, PKU can have severe consequences on an individual's health and development. The excessive levels of phenylalanine in the blood can cause intellectual disability, developmental delays, behavioral problems, seizures, and even psychiatric disorders. Therefore, early diagnosis through newborn screening programs and prompt initiation of treatment are crucial to prevent these complications.



New Mutations: In some cases, PKU can occur without a family history of the disorder. These cases are caused by new mutations in the PAH gene that arise spontaneously. These new mutations can be passed on to future generations if the affected individual has children.



Other Genetic Variants: While mutations in the PAH gene are the most common cause of PKU, there are rare cases where the disorder is caused by mutations in other genes involved in the production or recycling of tetrahydrobiopterin (BH4), a cofactor required for the PAH enzyme to function properly. These variants are known as BH4-responsive PKU or atypical PKU.



Environmental Factors: Although PKU is primarily a genetic disorder, certain environmental factors can influence its severity. For example, high temperatures, infections, stress, and other illnesses can temporarily increase phenylalanine levels in individuals with PKU, leading to symptoms such as irritability, poor concentration, and skin rashes. Additionally, pregnancy and hormonal changes can affect phenylalanine metabolism in women with PKU.



Conclusion: Phenylketonuria is primarily caused by genetic mutations in the PAH gene, resulting in the deficiency of the phenylalanine hydroxylase enzyme. This leads to the accumulation of phenylalanine in the body, which can have detrimental effects on an individual's health and development. Early diagnosis, newborn screening, and adherence to a phenylalanine-restricted diet are essential in managing PKU and preventing its associated complications.


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3 answers
PKU is an autosomal recessive metabolic genetic disorder. As an autosomal recessive disorder, two PKU alleles are required for an individual to exhibit symptoms of the disease. If both parents are carriers for PKU, there is a 25% chance any child they have will be born with the disorder, a 50% chance the child will be a carrier, and a 25% chance the child will neither develop nor be a carrier for the disease.

PKU is characterized by homozygous or compound heterozygous mutations in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine (Phe) to the amino acid tyrosine (Tyr). When PAH activity is reduced, phenylalanine accumulates and is converted into phenylpyruvate (also known as phenylketone), which can be detected in the urine.

Carriers of a single PKU allele do not exhibit symptoms of the disease but appear to be protected to some extent against the fungal toxin ochratoxin A. This accounts for the persistence of the allele in certain populations in that it confers a selective advantage—in other words, being a heterozygote is advantageous.

The PAH gene is located on chromosome 12 in the bands 12q22-q24.1. More than 400 disease-causing mutations have been found in the PAH gene. This is an example of allelic genetic heterogeneity.

Posted Feb 24, 2017 by Levi Christopher Lucero, Jr. 2185
Because you was a genetic trait inherited from trade carriers. My parents are both trade carriers I am the second of four children and I have PKU. Because my parents are both treat carriers they have a 25% chance of having a child with PKU and I happened to be at. If one parent is a trait carrier and the other is not there is a low chance of having a child with PKU.

Posted Sep 22, 2017 by Nickelle 2000

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Stories of Phenylketonuria

PHENYLKETONURIA STORIES
Phenylketonuria stories
Hello to everyone that reads! im currently 19 with a PKU toddler! he was born march 7th 2014. got a call on the 12th and then took a nice long ride a ccouple hundred miles away on the 14th to my son's pku clinic. they explained everything to me and h...
Phenylketonuria stories
I was a month old went the doctors  told my parents that I have pku. I'm 42 years old. I got married in 2005. To a really nice guy but in 2009 my husband passed away on February 13, 2009. At that time I went off diet for 5 years.  And it really mes...
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Found out my baby daughter has got PKU, still getting my head around it all
Phenylketonuria stories
Hi! I'm Andreia. I'm 28 years old. I'm from Portugal living in irland Since 2014. I was diagnosed when I was 12 days old. Still following my diet. My family did everything they could to give me all I needed. I'm a nurse now, have a job, starting my o...
Phenylketonuria stories
It's actually my children that have PKU. Both diagnosed within ten days of birth and doing very well. My daughter is now nearly ten and currently on 7.5 exc. per day. My son is 5 and on 7 exc. per day.  Both are treated at Bristol Childrens Hospit...

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