According to Virginia Schuett at PKU News PKU (phenylketonuria), in its “classic” form, is a rare, inherited metabolic disease that results in mental retardation and other neurological problems when treatment is not started within the first few weeks of life. When treatment is begun early and well-maintained, affected children can expect normal development and a normal life span. (Not all elevations of blood phenylalanine require treatment; any child with a level less than 6 mg/dl does not need to be on a special diet and is not risk for mental retardation.) Until recently, the only treatment was a very strict diet that limits the amino acid, phenylalanine. Now, however, there is a drug called Kuvan that can help in some cases.
PKU is carried through an "autosomal recessive" gene. This means that two people who conceive a child must both be "silent carriers" of the gene in order for there to be a chance that the baby will have PKU. When two carriers conceive a child, there is a one in four (or 25%) chance for each pregnancy that the baby will have PKU. The incidence of carriers in the general population is approximately one in fifty people, but the chance that two carriers will mate is only one in 2500. Carrier tests are available only through PKU treatment programs.
Over 500 different genetic mutations have been identified that result in defective functioning of the phenylalanine hydroxylase enzyme, resulting in elevated phenylalanine levels. Each different mutation or combination of mutations results in more or less enzyme activity in the effected person.
Diet. The diet for the most severe form of PKU, called “classic PKU,” eliminates all of the very high protein foods since all protein contains phenylalanine. This means that all concentrated sources of protein must be eliminated from the diet in order to limit the amount of phenylalanine. Except in rare circumstances, the diet does not allow consumption of meat, fish, poultry, milk, eggs, cheese, ice cream, legumes, nuts, or many products containing regular flour.
A synthetic formula is used as a nutritional substitute for the eliminated foods. This formula is very expensive. Fortunately, a number of states have mandated insurance coverage for the cost, or in some instances the state health department may provide the formula to families of affected children. There are many different formula options available now, from powders that mix with liquid (the traditional form) to pills and various flavored bars.
Brighit drinks only formula during the day, as well as eating fruits and vegetables and other low protein items. She eats a few regular foods that are lower in protein as well. She will have to be on this diet for her entire life, but she shows no signs of having any difficulties so we are thankful every day! While it was devastating at first, with time and perspective we realize that God actually blessed us because PKU is not life-threatening, just quality of life threatening.
