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Case Study: Phenylketonuria (PKU) - PowerPoint PPT Presentation
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Case Study: Phenylketonuria (PKU). Bobby Orr Adam Edwards Danielle Heinbaugh. Introduction: What is PKU?. PKU (Phenylketonuria) is a disorder defined as the inability to metabolize the essential amino acid phenylalanine
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Introduction: What is PKU?
- PKU (Phenylketonuria) is a disorder defined as the inability to metabolize the essential amino acid phenylalanine
- This can cause mental retardation, if untreated, although sufficient treatment can occur immediately after birth
Symptoms:
- The main symptom consists of mild to moderate mental retardation, but this is easily prevented through treatment
- However, other side effects include seizures, vomiting, a “mousy odor”, and behavioral self-mutilation
- In some cases, treatment can reduce or reverse the mental retartadtion
The Guthrie Test:
- determines the phenylalanine level in the blood
- should be done on the second or third day of life
- is a screening test done to identify elevated phenylalanine levels it is not diagnostic
- PKU babies’ phenylalanine level is usually 20-40 mg/dl in comparison with normal levels of 4-6 mg/dl.
How the Guthrie Test works:
- Blood on filter paper is placed on agar plates with a strain of bacillus subtilis that requires phenylalanine for growth.
- The presence of growth is indicated by a halo surrounding the filter paper.
- If positive, blood phenylalanine and tyrosine levels are determined, and if elevated, a confirmatory assay for phenylalanine hydroxylase is done.
- Inherited as autosomal recessive disorder.
- Variation to classical symptoms is result of compound heterogeneity.
- 65 allelic variants make compound heterogeneity more common then homogeneity for the same allele.
- Phenylketonuria is treatable with a low phenylalanine diet.
- phenylalanine levels should be kept below 15 mg per deciliter
- Nutra sweet is especially high in phenylalanines
Genetic Counseling:
- Tell the parents that the baby will be normal if they follow the prescribed dietary guidelines
- The child is normally out of danger of the disease after puberty
- Phenylalanine should be avoided
- Stay away from nutra sweet, meats, dairy products
