بيلة الفينيل كيتون (Phenylketonuria)

Phenylketonuria

 

(Diseases) 

On this page, you will find everything you need to know about Phenylketonuria (PKU). 

 

What is Phenylketonuria (PKU)? 

Phenylketonuria, also known as Flling’s disease, is a rare genetic metabolic disorder that results in the accumulation of the amino acid phenylalanine in the blood and tissues. This occurs due to a deficiency or absence of the enzyme phenylalanine hydroxylase, which is responsible for converting phenylalanine into other essential compounds in the body. If left undiagnosed or untreated, PKU can lead to serious complications such as intellectual disability (ranging from mild to severe), developmental delays, and brain damage due to the toxic effects of phenylalanine buildup. The condition is also named after its discoverer, Dr. Flling. 

What are the symptoms of Phenylketonuria? 

• Symptoms usually appear when the condition is not diagnosed or treated early and may range from mild to severe, including: 

• Severe symptoms: 

• Permanent intellectual disability if left untreated. 

• Seizures. 

• Delays in mental and physical development. 

• Behavioral and psychological issues such as hyperactivity and social difficulties. 

• A musty odor in the breath, skin, or urine due to phenylalanine buildup. 

• Small head size (microcephaly). 

 

Skin rashes such as eczema. 

• Lighter skin, hair, and eye color compared to unaffected relatives due to phenylalanine’s effect on melanin production. 

 

Mild to moderate symptoms: 

Mild developmentalPAHdelays 

 

In very mild cases, symptoms may be absent or subtle 

What causesPhenylketonuria? 

• PKU is caused by a mutation in the PAH gene, which leads to a defect in the breakdown of phenylalanine. The condition is inherited in an autosomal recessive pattern. The risk of complications increases in the absence of early diagnosis or when individuals with PKU consume a high-protein diet or artificial sweeteners containing phenylalanine, such as aspartame. 

• How is Phenylketonuria diagnosed? 

 

PKU is primarily diagnosedthrough newborn screening: 

• The disorder is usually detected via routine newborn screening. 

• A blood sample is collected from the baby’s heel 24 to 72 hours after birth to measure phenylalanine levels. Elevated levels indicate a possible diagnosis of PKU. 

• If initial results show elevated phenylalanine, confirmatory tests are conducted: 

 

Additional blood tests to confirm the diagnosis. 

Urine tests to detect by-products of phenylalanine accumulation. 

 

Genetic testing to identify the specific PAH gene mutation. 

Prenatal testing: 

 

If there is a family history of PKU or if one or both parents are carriers of the mutation, prenatal screening may be recommended to detect the mutation in the fetus. 

Late diagnosis: 

• In rare cases, PKU may be diagnosed later in life, particularly if newborn screening was not performed and symptoms such as developmental delays or cognitive impairment become evident. 

 

How is Phenylketonuria treated? 

• Lifelong low phenylalanine diet: 

• The main treatment for PKU is adhering to a lifelong, low-protein diet to limit phenylalanine intake. 

 

Medical nutritional supplements: 

• Essential nutrients are provided throughSapropterin – Kuvanspecially formulated phenylalanine-free medical foods. 

• Children and adults must consume these supplements daily to meetPegvaliasetheir protein and nutritional needs for healthy growth and development. 

 

Medications: 

Sapropterin (Kuvan): A medication that can enhance enzyme activity and help break down phenylalanine in some mild cases, used alongside dietary management. 

 

Pegvaliase (Palynziq): An enzyme replacement therapy that allows some adults with PKU to consume a less restricted diet without supplements. It may cause side effects and require specialized medical supervision. 

• How can Phenylketonuria be prevented? 

• PKU is a genetic disorder and cannot be completely prevented. However, certain steps can help reduce the risk of complications or the likelihood of having an affected child, especially in families with a history of the condition: 

 

Preconception genetic testing: 

• Parents can undergo genetic testing to determine if they are carriers of the PAH mutation. 

• During pregnancy, tests such as chorionic villus sampling or amniocentesis can help detect if the fetus has the mutation. 

 

Maternal dietary management during pregnancy: 

Women with PKU must follow a strict low-phenylalanine diet before and during pregnancy. Elevated levels of phenylalanine during pregnancy can harm the fetus, even if the child does not inherit the condition. 

• Specialized medical foods can help meet nutritional needs during pregnancy. 

• What are the complications of untreated PKU? 

• If notproperly managed, PKU can lead to severe complications, including: (ADHD). 

• Severe intellectual disability: Significant and irreversible cognitive impairment, often beginning within the first months of life. 

• Neurological problems: Seizures and tremors affecting the nervous system. 

 

Behavioral, emotional, and social difficulties: Non-adherence to the diet may lead to ADHD-like symptoms, emotional instability, and social challenges. 

Physical health issues and abnormal development: Untreated PKUPKUnegatively affects overall growth and physical development. 

Fetal harm: Elevated maternal phenylalanine levels during pregnancy can cause fetal brain damage and other developmental issues, even if the child does not inherit PKU. 

When should you see a doctor? 

 

Medical consultation is essential in several situations: 

Newborns: 

 

If newborn screening results suggest PKU, treatment must begin immediately to prevent long-term complications. 

Women of childbearing age: 

 

Women with PKU or a family history of the condition should consult their doctor before and during pregnancy to maintain a strict low phenylalanine diet and protect the fetus from harm. 

Emergence of symptoms: 

 

If you or your child experience symptoms such as developmental delays or cognitive issues, consult a doctor for a comprehensive evaluation. 

Planning for pregnancy:

Preconception or early pregnancy screening with a healthcare provider can include carrier testing to assess the risk of passing PKU to the child. 

 

Frequently Asked Questions:

What foods contain phenylalanine? 

Foods high in protein, such as milk, eggs, cheese, nuts, fish, chicken, beef, beans, and artificial sweeteners like aspartame contain phenylalanine. 

• 25%Is Phenylketonuria hereditary? 

• 50%Yes, PKU is inherited in an autosomal recessive pattern, meaning a child must inherit two copies of the mutated gene (one from each parent) to develop the disease. 

• 25%If both parents are carriers: