Phenylketonuria

Definition

Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase, which is crucial for the metabolism of the amino acid phenylalanine. This condition leads to the accumulation of phenylalanine in the body, which can result in severe neurological damage if left untreated. PKU is an example of an inherited metabolic disorder, highlighting the importance of genetic factors in the development of certain diseases.

5 Must Know Facts For Your Next Test

1. PKU affects approximately 1 in 10,000 to 15,000 newborns in the United States and is more common in certain populations.
2. Without early diagnosis and dietary intervention, individuals with PKU can suffer from intellectual disabilities, behavioral issues, and seizures due to high levels of phenylalanine.
3. Treatment for PKU typically involves a strict low-phenylalanine diet, avoiding high-protein foods like meat, dairy, and nuts while using specialized medical foods.
4. Gene therapy is being researched as a potential treatment for PKU, aiming to restore normal function to the faulty gene responsible for the disorder.
5. Ongoing monitoring of blood phenylalanine levels is critical for individuals with PKU to ensure they remain within safe limits and prevent neurological damage.

Review Questions

• How does the lack of phenylalanine hydroxylase lead to the symptoms associated with phenylketonuria?
  • The absence of phenylalanine hydroxylase impedes the conversion of phenylalanine into tyrosine, causing phenylalanine to accumulate in the body. This buildup is toxic to the brain and can lead to severe neurological symptoms such as cognitive impairment, behavioral problems, and seizures. Early diagnosis and treatment are crucial to prevent these symptoms from developing.
• Discuss the implications of autosomal recessive inheritance for individuals with phenylketonuria and their families.
  • Since PKU follows an autosomal recessive inheritance pattern, both parents must carry at least one copy of the defective gene for their child to develop the disorder. This means that siblings of affected individuals also have a 25% chance of being affected. Genetic counseling can help families understand their risks and make informed decisions about family planning and management strategies.
• Evaluate the role of newborn screening programs in managing phenylketonuria and improving outcomes for affected infants.
  • Newborn screening programs are vital in managing PKU because they allow for early detection and intervention before symptoms develop. By testing infants shortly after birth, healthcare providers can identify those at risk and implement dietary restrictions immediately. This proactive approach has significantly improved outcomes for individuals with PKU, reducing intellectual disability rates and promoting healthier lives through proper management.

Related terms

Phenylalanine: An essential amino acid that must be obtained through diet; it is a building block for proteins and can be toxic in high amounts for individuals with PKU.

Autosomal recessive inheritance: A mode of genetic inheritance where two copies of an abnormal gene must be present for the disease or trait to develop, as seen in PKU.

Newborn screening: A public health program that tests infants shortly after birth for various genetic, endocrine, and metabolic disorders, including PKU, to enable early diagnosis and treatment.