FENILCETONÚRIA

Summary

This video lesson explains phenylketonuria (PKU), a rare genetic and metabolic disorder. It affects one in every 25,000 births, primarily in Europe and the U.S. PKU results from a mutation in the gene responsible for producing the enzyme phenylalanine hydroxylase, which breaks down phenylalanine found in protein-rich foods. Without this enzyme, phenylalanine accumulates, leading to severe brain damage. Symptoms include intellectual disabilities, seizures, delayed development, and distinctive body odor. Treatment involves a strict low-protein diet and, in some cases, enzyme replacement therapy. Early diagnosis through newborn screening is crucial for managing the condition.

Takeaways

• 😀 PKU (Phenylketonuria) is a rare genetic metabolic disorder affecting about 1 in 25,000 births, more common in Europe and the United States than in South America.
• 😀 PKU occurs due to a mutation in the gene responsible for producing the enzyme phenylalanine hydroxylase, which breaks down the amino acid phenylalanine.
• 😀 When phenylalanine hydroxylase is deficient, phenylalanine builds up in the body and becomes toxic to the central nervous system, causing neurological damage.
• 😀 High levels of phenylalanine can lead to intellectual disabilities, seizures, developmental delays, and a strong, unpleasant body odor.
• 😀 PKU is inherited from both parents who carry the mutated gene, and early diagnosis is crucial for effective treatment.
• 😀 Treatment for PKU involves a strict, low-protein diet to limit phenylalanine intake, along with possible supplementation with tyrosine and enzyme replacement therapies.
• 😀 The 'teste do pezinho' (heel prick test) is mandatory in Brazil for early PKU detection and has been since 2001.
• 😀 If not diagnosed and treated early, individuals with PKU can suffer from severe developmental issues, including brain damage.
• 😀 Experimental treatments, such as enzyme replacement therapy, aim to support the body's ability to break down phenylalanine and improve health outcomes.
• 😀 There is a need for government intervention to make PKU-friendly foods more affordable and accessible to families managing the condition.

Q & A

What is Phenylketonuria (PKU)?

Phenylketonuria (PKU) is a rare genetic metabolic disorder in which individuals have a mutation in a gene that affects an enzyme called phenylalanine hydroxylase, which is responsible for breaking down the amino acid phenylalanine. Without this enzyme, phenylalanine builds up and becomes toxic to the nervous system.

How common is Phenylketonuria?

Phenylketonuria is extremely rare, affecting approximately 1 in 25,000 births. It is more common in Europe and the United States, and less common in South American countries.

What causes the toxicity in PKU?

The toxicity occurs when phenylalanine, a type of amino acid found in protein-rich foods, accumulates in the body due to the lack of the enzyme phenylalanine hydroxylase, which normally breaks it down. This excess phenylalanine becomes toxic to the central nervous system.

What are the primary symptoms of Phenylketonuria?

Symptoms of PKU include intellectual disability, seizures, developmental delays, body odor due to high levels of phenylalanine, distinctive urine smell, skin discoloration, and microcephaly (small head size).

How does the mutation in PKU affect enzyme function?

In PKU, a genetic mutation causes the enzyme phenylalanine hydroxylase to be deficient or non-functional, preventing the proper breakdown of phenylalanine, which leads to its accumulation in the body and subsequent damage to the brain and nervous system.

What role does tyrosine play in the body, and why is it important in PKU?

Tyrosine is an amino acid formed when phenylalanine is metabolized by the enzyme phenylalanine hydroxylase. Tyrosine is crucial for the production of neurotransmitters and thyroid hormones, which regulate metabolism and cognitive functions. In PKU, the lack of phenylalanine hydroxylase disrupts this process.

How is PKU diagnosed?

PKU is diagnosed through the mandatory newborn screening test, commonly known as the 'heel prick' test or 'teste do pezinho' in Brazil. This test detects elevated levels of phenylalanine in the blood, allowing for early diagnosis and intervention.

What is the treatment for Phenylketonuria?

The primary treatment for PKU is a low-protein diet, which severely restricts foods rich in phenylalanine, such as meat, eggs, milk, and chocolate. In some cases, enzyme replacement therapy and the administration of tyrosine may be used to help manage the condition.

What dietary changes are recommended for individuals with PKU?

Individuals with PKU must follow a low-protein diet to avoid high levels of phenylalanine. This includes limiting or avoiding foods like eggs, milk, and meat. Special foods that are phenylalanine-free or low in phenylalanine are available but can be expensive.

Why is early diagnosis important in managing PKU?

Early diagnosis is crucial because untreated PKU can lead to severe intellectual disability and neurological damage. By identifying PKU early through newborn screening, treatment can begin promptly, preventing or minimizing brain damage and improving long-term outcomes.