Phenylketonuria (PKU)

Phenylketonuria

(PKU)

PKU is an inherited disease, starting with the parents. Each parent has two PAH genes which are located on each chromosome 12. In order to pass this genetic disease down, each parent needs to have a mutated PAH gene. This is because this disease is a autosomal recessive disorder which means in order for a child to inherit it, it needs to have two copies of the mutated gene. While producing sperm or eggs, only one of the parent's PAH genes goes into each cell, resulting in which about half of the cells would contain a mutated PAH. The offspring of who's parents are each carriers of the mutated gene would have a 1/4 chance of obtaining PKU. The child could still have one mutated PAH gene, which would make him/her a carrier, but the child does not actually have the disease unless it has both mutated genes, which is what makes this disease autosomal recessive.

Signs and Symptoms

New born babies usually do not have any signs/symptoms of this disease at first, but if not treated, it can lead to serious brain damage causing behavioral problems, epilepsy, and stunt growth of the baby. Physical symptoms can include:

• a small head
• fair skin
• eczema
• body odor

Diagnosis

PKU must be treated early, therefore every baby in the United States gets tested for this disease. What they look for in a PKU-positive baby is high levels phenylalanine in their system. They do this by a simple blood test of the baby's heel or arm. Because all babies are tested and treatment is started right away, severe symptoms of PKU are rarely seen.

Treatments

Mostly all types of protein contain phenylalanine in them, which is why people with PKU obtain a protein-free diet. As for infants, they are given a protein-free formula. People with PKU also can't have artificial sweeteners because those also contain phenylalanine. Besides having a strict diet, another treatment for PKU is an FDA approved medicine.

Prevalence in Population

Prevalence of PKU varies through ethnicity and geographic regions worldwide. In the US, PKU occurs in 1 in 10,000 to 15,000 newborns. As far as ethnicity, the groups that have higher rates are Turks, which are 1 in 2,600, and Irish, which are 1 in 4,5000. The ethnic group that has a significantly low rate of PKU is Japanese, which is 1 in 143,000. This disorder is not seen very much in Africans as well.

Life Expectancy

A person with PKU has almost the same lifespan as somebody without PKU, as long as they had followed the appropriate steps to treat their PKU correctly. This is especially important during their childhood when the brain is still developing.