PKU Phenylketonuria Case Studies

Intro: PKU (Phenylketonuria) is a genetic disorder where the body lacks a certain enzyme which breaks down PHE, which in turn leads to dangerous build up of PHE.

History:

PKU was discovered in 1934 in Norway by Dr. Asbjørn Følling. A mom of two kids came to him in dire need of help after being denied by many doctors. She was denied because the doctors failed to realize what was wrong with the children. He was told of their unusual appetites and behaviors and was unable to come up with a diagnosis until he tested their urine. (PKU News, 2016) He tested for ketones by adding ferric acid to their urine, and he noticed that it turned green. Typically, it turns brown if it's normal and purple if ketones are present. This had never been discovered before, and he ended up concluding that their was an unknown substance present in the children’s urine. Upon testing them, he found out that it was phenylpyruvic acid by comparing the unknown substance to phenylpyruvic acid. The melting points were the same, leading him to the
This means both parents carry the copy of the mutated gene. Because both copies are needed, the parents aren't affected. In each parents PAH gene, there is a mutation. This happens on the 12th chromosome. Since only half of their PAH genes are affected, only half of the sperm cells and half of the eggs will have the mutated gene. If both the sperm and the egg have the mutation, the child may be born with PKU. If only one of the mutated genes is passed on, the child will be a carrier. PKU is a recessive disorder and needs both mutated PAH genes in order for the child to exhibit symptoms.The child has a 1 in 4 chance of inheriting PKU, assuming both parents are carriers. USually, children who are born with PKU have parents who were unaware that they were carriers. (National Human Genome Research Institute, 2014) (Your Genes, Your Health, 2016) (Mayo Clinic,