SNP Shot: Genomic Insights

Phenylketonuria (PKU) is a genetic condition where the body can't properly process phenylalanine, an amino acid found in many foods. Phenylalanine comes from protein-rich foods like meat, eggs, nuts, and milk, as well as some artificial sweeteners. Without treatment, phenylalanine builds up in the blood to dangerous levels, potentially leading to intellectual disabilities and other serious health issues.

PKU symptoms range in severity. The most severe form, classic PKU, often shows no signs in newborns for the first few months. However, if untreated, these children will develop permanent intellectual disability. Other common problems include seizures, developmental delays, behavioral issues, and psychiatric disorders. A characteristic musty or mouse-like odor can also occur due to excess phenylalanine. Children with classic PKU often have lighter skin and hair than their relatives and may also develop skin conditions like eczema.

Less severe forms of PKU, such as variant PKU and non-PKU hyperphenylalaninemia, carry a lower risk of brain damage. Some people with very mild cases may not need treatment at all.

Managing PKU often involves a strict diet low in phenylalanine. Since phenylalanine is in all proteins, the PKU diet requires avoiding high-protein foods like meat, dairy, nuts, and tofu. Infants with PKU require special low-protein formulas. Individuals are often limited to specific fruits, vegetables, and foods high in fats and sugars like butter, jelly, pasta, and potato chips. Aspartame, an artificial sweetener in diet soda and other low-calorie products, should be avoided due to its high phenylalanine content. The safe amount of phenylalanine varies from person to person, so working with a healthcare professional to create a personalized diet is crucial.

Babies born to mothers with PKU who aren't following a low-phenylalanine diet are at a high risk of intellectual disability due to exposure to high phenylalanine levels before birth. These infants may also have low birth weights, slower growth, heart defects or other heart problems, an abnormally small head (microcephaly), and behavioral problems. Mothers with PKU who aren't on a low-phenylalanine diet also face a higher risk of pregnancy loss.

Inheritance:

PKU follows an autosomal recessive inheritance pattern. This means that for a person to have PKU, they must inherit two copies of the mutated gene, one from each parent. The parents are carriers, each having one copy of the mutated gene, but they typically don't show any symptoms of PKU themselves.