Phenylketonuria


 * PKU **

Phenylketonuria is an inherited disorder that increases the levels of a substance called phenylanine. 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 sweetners. If PKU is not treated, phenylalanine can build up to harmful levels in the body, causing intellectual disability and other serious health problems.


 * Symptoms of PKU are:
 * infants with classic PKU appear normal until they are a few months old.
 * Without treatment with a special low-phenylalanine diet, these children develop permanent intellectual disability.
 * Seizures, delayed development, behavioral problems, and psychiatric disorders are also common.
 * Untreated individuals may have a musty or mouse-like odor as a side effect of excess phenylalanine in the body.
 * Children with classic PKU tend to have lighter skin and hair than unaffected family members and are also likely to have skin disorders such as eczema.


 * Type of genetic mutation:
 * The Chromosome that is affected in PKU is 12q 22-24


 * Cause:
 * A genetic mutation causes PKU. The defective gene contains the instructions for making an enzyme needed to process the amino acid called phenylalanine.


 * Epidemiology:
 * Usually PKU has an incidence of around 1 in 20,000 newborns. The highest incidence of PKU is seen among white infants of European descent (1/5,000 to 1/15,000 births). An exception is Finland, where the disorder is extremely rare (1/200,000 births). Black, Asian, and Hispanic infants are less commonly affected. Newborn screening programs were initiated in developed countries in the mid- to late 1960s and, therefore, most patients receiving treatment are younger than 40 years of age. Most patients born before that time are mentally retarded and institutionalized.


 * Diagnosis:
 * Newborn blood testing identifies almost all cases of PKU.


 * Prognosis:
 * The outlook depends on how early an infant with PKU is diagnosed and begins the special diet. It also depends on how strictly and consistently the diet is followed throughout life. Infants with PKU who are identified within the first few days after birth and are put on a strict diet before 3 weeks of age have the best prognosis.


 * Treatment:
 * The main PKU treatment is a strict diet with very limited intake of phenylalanine, which is mostly found in foods containing protein.