Classic PKU, moderate or variant PKU and mild PKU.
Phenylketonuria (commonly known as PKU) is an inherited disorder that increases the levels of a substance called phenylalanine in the blood. Phenylalanine is a building block of proteins (an amino acid) that is obtained through the diet. It is found in all proteins and in some artificial sweeteners. The most severe form of this disorder is known as classic PKU. Infants with classic PKU appear normal until they are a few months old. Without treatment, these children develop permanent intellectual disability. Seizures, delayed development, behavioral problems, and psychiatric disorders are also common. During adolescence through young adulthood, testing may be conducted twice a year. In adulthood, yearly testing will likely continue for life.Types of Phenylketonuria (PKU)PKU is separated into two types: classic PKU and moderate PKU. These two types refer to different levels of blood Phe. A person with moderate PKU has lower blood Phe levels than a person with classic PKU.  Phenylketonuria (PKU) can be defined as a rare metabolic disorder caused by a deficiency in the production of the hepatic (liver) enzyme phenylalanine hydroxylase (PAH). Abbr. PKU A genetic disorder in which the body lacks the enzyme necessary to metabolize phenylalanine to tyrosine. Left untreated, the disorder can cause brain damage and progressive mental retardation as a result of the accumulation of phenylalanine and its breakdown products. Phenylketonuria (PKU) (phenyl + ketone + -uria; /ˌfinəlˌkitɵnˈjʊəriə/) is an inborn error of metabolism involving impaired metabolism of phenylalanine, one of the amino acids. Phenylketonuria is caused by absent or virtually absent phenylalanine hydroxylase (PAH) enzyme activity. In people without PKU, the PAH enzyme breaks down any excess phenylalanine from these sources beyond what is needed by the body. However, if there is not enough of the PAH enzyme or its cofactor, then phenylalanine can build up in the blood and brain to toxic levels, affecting brain development and function. The genetics of PKU. Genes are present in every cell in the body. They provide the blueprint for each trait we have, such as eye color and height. Genes also carry the instructions to make the enzymes our bodies need to break down amino acids such as Phe into building blocks. For a person to have PKU, both the mother and the father must pass on the mutated phenylalanine hydroxylase (PAH) gene. Each parent is a “carrier” because he or she carries one copy of the mutated, disease­–causing gene and one copy of the nonmutated gene. People who are carriers of the PKU gene have no known symptoms. Depending on the level of phenylalanine and tolerance for phenylalanine in the diet, PKU is classified into two different types: classic, which is the severe form, and moderate. Children and adults who are treated early and consistently develop normally. Depending on the level of phenylalanine and tolerance for phenylalanine in the diet, PKU is classified into two different types: classic, which is the severe form, and moderate. Therefore, each patient needs an individualized treatment plan. Genetic mutation. PKU is caused by a genetic mutation (change to the DNA) in the human phenylalanine hydroxylase (PAH) gene. There are many different types of mutations that can affect the PAH gene, all of which result in the body not producing a functioning PAH enzyme. People with PKU can have different levels of PAH deficiency, resulting in differences in Phe levels and symptoms. Different PKU levels are sometimes classified as classic PKU, moderate or variant PKU, mild PKU, or hyperphenylalaninemia. 3. Based on blood Phe levels at diagnosis, there are 4 levels of PKU severity 3 1  : Hyperphenylalaninemia, with Phe levels that are slightly above normal range: 120-600 µmol/L (2-10 mg/dL). For a person to have PKU, both the mother and the father must pass on the mutated phenylalanine hydroxylase (PAH) gene. Each parent is a “carrier” because he or she carries one copy of the mutated, disease­–causing gene and one copy of the nonmutated gene. People who are carriers of the PKU gene have no known symptoms. Phenylketonuria (PKU) is a condition in which the body cannot break down one of the amino acids found in proteins. PKU is considered an amino acid condition because people with PKU cannot break down the amino acid called phenylalanine. If left untreated, PKU can cause brain damage or even death. Other enzymes break down these amino acids. In classic phenylketonuria (PKU), the enzyme phenylalanine hydroxylase (PAH) is not working correctly. PAH’s job is to break down the amino aci PKU is a disease caused by the liver's inability to produce a particular type of PAH enzyme. This enzyme converts (metabolizes) the amino acid called phenylalanine into another amino acid, tyrosine. This is the only role of PAH in the body. Abbr. PKU A genetic disorder in which the body lacks the enzyme necessary to metabolize phenylalanine to tyrosine. Left untreated, the disorder can cause brain damage and progressive mental retardation as a result of the accumulation of phenylalanine and its breakdown products.
http://ghr.nlm.nih.gov/condition/phenylketonuria http://www.brighttots.com/Developmental_disorders/Phenylketonuria-PKU.html http://medical-dictionary.thefreedictionary.com/Phenylketonuria https://en.wikipedia.org/wiki/Phenylketonuria http://www.pku.com/understanding-pku/causes-and-types-of-pku/ http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024675/ http://www.nhs.uk/conditions/Phenylketonuria/Pages/Causes.aspx http://www.pku.com/understanding-pku/causes-and-types-of-pku/ http://www.babysfirsttest.org/newborn-screening/conditions/classic-phenylketonuria-pku http://medical-dictionary.thefreedictionary.com/Phenylketonuria
different types of pku