1. Case Study: Phenylketonuria (PKU)
Bobby Orr
Adam Edwards
Danielle Heinbaugh

2. 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

3. 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

4. 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 mg/dl in comparison with normal levels of 4-6 mg/dl.

5. 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.

6. PKU Inheritance: 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.

7. Treatment of PKU:
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

8. 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