A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

Amino acid: A class of organic molecules that make up the building blocks of all proteins. There are 20 amino acids that are considered standard, and of those, 10 are considered essential components of a healthy diet because they cannot be produced in the human body. These 10 essential amino acids are phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, arginine, leucine, and lysine.

Because phenylalanine is one of the essential amino acids, everyone, including people with phenylketonuria (PKU), must have it as part of their diet.

B

BH4: See tetrahydrobiopterin.

BPPS: BioMarin Patient and Physician Support is a program that can work with your insurance company to help obtain coverage for KUVAN, and help you research insurance coverage if you don’t already have it. BPPS is also your gateway to other patient services that can help you obtain KUVAN. See BPPS.

C

Classic PKU: The most severe form of phenylketonuria (PKU). People with classic PKU typically have a blood phenylalanine (Phe) level of >1200 μmol/L when not on a low-Phe diet and typically tolerate less than 250–350 mg of dietary Phe (about 17–23 exchanges) a day.

Cofactor: A molecule that must work with an enzyme in order for that enzyme to function.

E

Enzyme: A kind of biological molecule that facilitates certain chemical reactions inside the body. The human body contains many thousands of different enzymes, which are involved in virtually every aspect of the body’s functions. People with phenylketonuria (PKU) lack a certain enzyme called phenylalanine hydroxylase (PAH).

G

Gene: A region of deoxyribonucleic acid (DNA) that codes for a specific characteristic. When a gene mutates, it may no longer perform the same function, and often the mutation renders it entirely inactive. In the case of phenylketonuria (PKU), the gene involved in the production of phenylalanine hydroxylase is mutated, causing the liver to produce insufficient amounts of that enzyme, and thus restricting the activity of the metabolic pathway that converts phenylalanine to tyrosine.

Genetic counselor: A healthcare professional who specializes in the education and support of patients and families regarding inherited diseases. The genetic counselor can also speak with prospective parents on inherited diseases to which their offspring may be susceptible.

H

Hyperphenylalaninemia: Abnormally high levels of phenylalanine in the blood. This is a sign of phenylketonuria (PKU), but could also be found in several other conditions. The newborn screening test is technically a test for hyperphenylalaninemia rather than for PKU. In other words, if a newborn tests positive in the first screening, all it means is that the newborn has a high level of phenylalanine in his or her blood, which may or may not be due to PKU. This means additional testing is required to learn what is causing hyperphenylalaninemia. People with mild hyperphenylalaninemia have a blood Phe level of <600 μmol/L when not on a low-Phe diet.

I

Inborn error of metabolism: Category of diseases affecting metabolism, which are inherited through genes and originate at birth. Phenylketonuria (PKU), albinism, congenital hypothyroidism, tyrosinemia, and maple syrup urine disease are a few examples of inborn errors of metabolism.

K

K-PAP: The KUVAN Patient Assistance Program is a program of last resort for patients who do not have insurance coverage for KUVAN. See K-PAP.

M

Metabolic clinic: A medical facility often associated with a university or major hospital that specializes in treating people who have diseases of metabolism such as phenylketonuria (PKU). The clinic is likely to be operated by a metabolic geneticist, who oversees a staff of registered dietitians, genetic counselors, and other healthcare professionals.

Metabolic clinics have a substantial role in the treatment of PKU. Staff at a metabolic clinic will be responsible for periodic blood testing and checkups, nutritional advice, formula prescriptions, and, in some cases, psychological assessment.

Metabolic geneticist: A doctor specializing in inherited metabolic diseases. Each metabolic clinic has at least one of these specialists on staff, whose responsibilities include tracking patient history, interpreting blood tests, and prescribing phenylketonuria (PKU) formula.

Metabolism/Metabolize: The word metabolism refers to any chemical process that occurs within cells and the body and is necessary for the normal growth and functioning of the cell and the body. To metabolize means to carry out that process.

In the case of PKU, “metabolism” refers to the process by which phenylalanine is converted to tyrosine in the liver (eg, “phenylalanine metabolism,” “the metabolism of phenylalanine,” “phenylalanine is metabolized”).

Mild PKU: A less severe form of phenylketonuria (PKU) that may still cause mental retardation if not managed with a restricted diet. People with mild PKU have a blood Phe level of 600–1200 μmol/L when not on a low-Phe diet and tolerate about 350–400 mg of dietary phenylalanine (about 23–27 exchanges) a day.

N

Neurotoxic: Damaging to the brain. A “neurotoxin” is a substance or agent determined to be neurotoxic.

P

PAH: See phenylalanine hydroxylase.

Phenylalanine (Phe): A building block of protein, and one of the 10 essential amino acids. An inability to metabolize excess phenylalanine is the characteristic feature of phenylketonuria (PKU). When the blood concentration of phenylalanine exceeds what is considered a healthy level, excess amounts may build up in the brain, causing mental retardation.

Phenylalanine hydroxylase(PAH): An enzyme essential in the metabolism of phenylalanine, whose deficiency is the biochemical hallmark of phenylketonuria (PKU). Phenylalanine hydroxylase functions together with an enzyme cofactor, tetrahydrobiopterin (BH4), to convert phenylalanine to tyrosine in the liver.

Phenylketonuria (PKU): An inherited metabolic defect in protein metabolism. In PKU, the phenylalanine hydroxylase (PAH) enzyme is unable to convert phenylalanine to tyrosine, resulting in a buildup of phenylalanine (Phe) in the blood that eventually passes into the brain, causing mental retardation and other neurological problems.

R

Registered dietitian: A medical expert whose focus is diet and nutrition, and one of the key players in an individual’s management of phenylketonuria (PKU). A metabolic clinic is typically manned by a staff of registered dietitians overseen by a few metabolic geneticists. The registered dietitians are responsible for tracking the nutritional needs of PKU patients and recommending dietary changes when appropriate.

S

Specialty pharmacies: Specialty pharmacies dispense medications that require specialized delivery, storage, or patient dosing instructions, and ship the medications directly to the patient’s home. See specialty pharmacies.

T

Tetrahydrobiopterin (BH4): An enzyme cofactor that works together with phenylalanine hydroxylase to convert phenylalanine to tyrosine in the liver. Without the action of both phenylalanine hydroxylase and tetrahydrobiopterin, the chemical process cannot take place.

Tyrosine (Tyr): An amino acid. The phenylalanine hydroxylase (PAH) enzyme normally converts phenylalanine (Phe) to Tyr.