Guide to PKU - Mead Johnson Nutrition

Glossary Of TermsAssociated With PKUAmino acids are building blocksof proteins. Phenylalanine and tyrosineare amino acids. Some aminoacids are made by the body, but“essential” amino acids are not andmust be supplied in the diet. Phenylalanineis an essential amino acid.Autosomal recessive is a form ofinheritance requiring the presence oftwo genes for a trait in order for theindividual to show the trait. Personswith only one of an autosomal recessivegene pair are carriers of the traitbut are unaffected by the trait.Blood levels of phenylalanine aredetermined by tests done on bloodafter it is drawn from the heel, toe, orfinger. Blood levels of phenylalanineshould be in the range of 120-360umol/L (2-6 mg/dL).Collaborative study is a researchstudy on PKU. Because no one clinicin the country has enough patientswith PKU to answer all the questionswe have about the disorder, severalmajor medical centers collaborated ingathering data to learn more aboutPKU and improve treatmentmethods. This long-term projectdetermined much of what we nowknow about PKU, and researchcontinues at many PKU clinics.Enzymes are proteins responsiblefor causing or speeding up biochemicalreactions without being alteredthemselves by the reactions. Theenzyme phenylalanine hydroxylasecauses phenylalanine to be brokendown into tyrosine.Equivalent or exchange is ameasured amount of food, such ascereal, vegetable, or fruit, that hasa certain amount of phenylalanine.Some clinics use an “exchange”system to calculate intake ofphenylalanine. An “exchange”contains approximately 15 milligramsof phenylalanine. Patients on dietsfor treatment of PKU should eat alimited number of exchanges per day,determined in consultation with theirnutritionist and based on their sizeand growth needs.Genetics is the study of howcharacteristics are inherited. Genescontain information the body uses toproduce a specific trait or to performa particular body function.Growth measurements help youand the PKU clinic team know thatyour child is growing properly. Thesemeasurements are made at varioustimes for all children, not just forchildren with PKU. They typicallyinclude measures of your child’s height,weight, and head circumference.Guthrie test is a blood test usedin screening for PKU; newbornscreening is mandatory in the UnitedStates. It does not actually diagnoseyour child with PKU, but it indicatesto the physician that your child has ahigh probability of having PKU.Further tests are needed to make adefinite diagnosis.Hyperphenylalaninemiais a term meaning high levels ofphenylalanine in the blood. It21is a group of disorders in whichelevated blood phenylalanine levels area primary characteristic.Phenylalanine is one of severalamino acids that make up proteins.A certain amount of phenylalanineis needed for normal growth anddevelopment. Because the bodycannot make phenylalanine, it mustbe supplied in the diet. Phenylalanineis an “essential” amino acid.Phenylketonuria (PKU) is aninherited disorder in which the bodylacks the enzyme needed to convertphenylalanine to tyrosine. In PKU,excess phenylalanine accumulates inthe blood and tissues and can damagethe brain and nervous system ifleft untreated.Tyrosine is an amino acid whichis needed for normal growth anddevelopment. It is typically madeby the body from phenylalanine, butthe person with PKU can’t make thisamino acid and must get it from hisdiet. Tyrosine is present in phenylalanine-freeformulas suchas Phenyl-Free ® 1, Phenyl-Free 2,and Phenyl-Free 2HP.