Untreated phenylketonuria in infants can have devastating effects, such as seizures, metal retardation, tremors, stunted growth and eczema, reports Dr. George Krucik. If an adult phenylketonuric ingests sufficient quantities of phenylalanine, seizures and muscle pains result, adds Dr. Tracy Beck.
PKU is a genetically inherited metabolic disorder, and is characterized by a lack of the enzyme responsible for digesting the amino acid phenylalanine, according to Dr. Beck. If a phenylketonuric does not consume protein sources low in phenylalanine, phenylpyruvic acid builds up in the person's bloodstream. Phenylpyruvic acid primarily affects the brain, and thus high levels of this substance cause mental retardation, stunted growth, and seizures in phenylketonurics, reports Dr. Beck. In addition, people with untreated PKU display a loss of pigmentation, resulting in blond hair, blue eyes and a pale skin tone. Other skin issues can arise, such as eczema, adds Dr. Krucik. In addition to these symptoms, infants with PKU usually have a distinct musty odor from their breath, urine or skin.
As very few natural sources of protein are low in phenylalanine, phenylketonurics must follow a low-protein diet and drink a formulated protein blend. Phenylalanine is commonly found in artificial sweeteners, most commonly in diet colas, Dr. Beck notes.