Phenylketonuria (PKU) is an inherited disorder screened for at birth and currently there is no cure.  Those with PKU are born without an enzyme necessary to process phenylalanine, one of the essential amino acids present in all natural proteins.  The only effective treatment is to adhere to a strict low-protein diet and include special low-protein medical foods and formula.  People with PKU cannot eat many of the foods others take for granted, such as beef, pork, fish, poultry, peanut butter, cheese, milk, yogurt, eggs, and nuts.  Starchy foods such as cereals, pasta, rice, crackers, and bread must be low-protein versions.  All food must be weighed and measured each day.  People with PKU visit their medical teams as frequently as once a month, or twice a year, (depending on their age) to check blood work and monitor development.  If untreated, PKU can affect brain development and learning and cause neurological disorders.