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Questions and Answers
What are aminoacidopathies?
A class of inherited errors of metabolism involving enzyme defects inhibiting the body's ability to metabolize certain amino acids.
What is the cause of phenylketonuria (PKU)?
Phenylalanine hydroxylase (PAH) deficiency.
What is the estimated occurrence of phenylketonuria?
1 in every 15,000 births.
What are the consequences of lacking the enzyme phenylalanine hydroxylase in phenylketonuria?
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What are the consequences of phenylalanine hydroxylase (PAH) deficiency in phenylketonuria?
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What are some examples of aminoacidopathies?
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What is the characteristic odor of urine in patients with PKU?
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What is the goal of PKU treatment in terms of maintaining blood levels of phenylalanine?
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What is the first drug approved by the US FDA to help manage PKU?
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What is the sensitivity range of the Guthrie Bacterial Inhibition Test for PKU?
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What is the significance of tetrahydrobiopterin in PKU?
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What is the range of phenylalanine levels in patients with Non-PKU mild hyperphenylalaninemia?
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How can brain damage be avoided in PKU patients?
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What is the purpose of the Ferric Chloride Tube Test for PKU?
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What is the main cause of elevated blood levels of phenylalanine in PKU?
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What is the prevalence of cases of elevated phenylalanine levels that are not the result of the lack of the PAH enzyme?
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Study Notes
Aminoacidopathies
- Aminoacidopathies are genetic disorders characterized by a malfunction in the metabolism of amino acids.
- They often result from enzyme deficiencies that lead to the accumulation of specific amino acids in the blood.
Phenylketonuria (PKU)
- PKU is caused by a deficiency of the enzyme phenylalanine hydroxylase (PAH), which is essential for converting phenylalanine into tyrosine.
- Estimated occurrence of PKU is about 1 in 10,000 to 1 in 15,000 live births, varying by ethnicity and geographical location.
Consequences of PAH Deficiency
- Lack of PAH leads to elevated levels of phenylalanine, which can cause severe neurological damage if untreated.
- Without treatment, patients can experience developmental delays, intellectual disabilities, and behavioral problems.
Examples of Aminoacidopathies
- Common examples include Phenylketonuria (PKU), Maple Syrup Urine Disease (MSUD), and Tyrosinemia.
Characteristic Odor of Urine in PKU
- Patients with PKU typically have urine that smells musty or "mousy" due to the accumulation of phenylacetate.
PKU Treatment Goals
- The primary goal of PKU treatment is to maintain blood phenylalanine levels below 6 mg/dL to prevent toxicity and neurological damage.
First Drug for PKU Management
- Sapropterin dihydrochloride is the first drug approved by the US FDA to aid in managing PKU by enhancing the activity of the PAH enzyme.
Guthrie Bacterial Inhibition Test
- This test has a sensitivity range of approximately 90-100% for detecting PKU in newborns.
Tetrahydrobiopterin in PKU
- Tetrahydrobiopterin is a cofactor for PAH; its supplementation can help improve phenylalanine metabolism in some patients with PKU.
Non-PKU Mild Hyperphenylalaninemia
- Phenylalanine levels in patients with Non-PKU mild hyperphenylalaninemia typically range from 2-6 mg/dL.
Avoiding Brain Damage in PKU Patients
- Early diagnosis and strict dietary management can prevent brain damage in individuals with PKU.
Ferric Chloride Tube Test for PKU
- This test helps identify the presence of phenylketones in urine, indicating problems in phenylalanine metabolism.
Main Cause of Elevated Phenylalanine Levels
- The primary cause of elevated blood phenylalanine levels in PKU patients is the deficiency of the PAH enzyme.
Prevalence of Elevated Phenylalanine Levels
- Elevated phenylalanine levels can also occur in cases unrelated to PAH deficiency, such as other metabolic disorders or enzyme deficiencies.
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Description
Test your knowledge on aminoacidopathies, a class of inherited errors of metabolism which inhibit the body's ability to metabolize certain amino acids due to enzyme defects. Learn about diseases like phenylketonuria (PKU), tyrosinemia, alkaptonuria, and maple syrup urine disease.
