Phenylketonuria

Abstract

This paper describes about the serious disabling disease, known as Phenylketonuria . This is a rare disease, affects only minority of people. It detection is very essential at birth. Untreated cases may cause mental retardation and various abnormalities. Therefore, it detection is very essential to treat these patients. The paper explains about the disease, its prevalence, its signs, and symptoms, its genetic causes and its phenotypes. This also explains about its screening and treatment.

Phenylketonuria

Introduction

It is an autosomal recessive genetic disease, occurs due to mutations of gene coding for the enzyme phenylalanine hydroxylase. This enzyme converts phenylalanine to tyrosine. When its level is reduced, phenylalanine is converted into phenylketone and excreted in urine (Centerwall, & Centerwall, 2000). Untreated PKU cause mental retardation and other conditions. The main treatment is a strict restricted diet. Patients who maintain strict diet usually have a normal mental development. The neurocognitive development, quality of life and growth can be abnormal l if the diet is not maintained.

Phenylketonuria was first discovered in 1934 by Ivar Asbjørn Følling. He noticed that excess phenylalaninemia was causing mental retardation. The disease is also called as Følling's disease. He applied chemical analysis to the study. He analysed urine sample of patients along with him many other physicians tested urine of other patients (Gonzalez, & Willis, 2010).

Discussion

Phenylketonuria is an autosomal recessive disease, occurring at the rate of in 15,000 people in US. This disease is more common in whites than in blacks and Asians. The disease occurs due to accumulation of the amino acid called as phenylalanine in the body tissues. This occurs due to an absence of phenylalanine hydroxylase . This enzyme is necessary to convert phenylalanine to tyrosine. If there is absence of PAH, the phenylalanine cannot be metabolized and accumulates in the tissues. The normal level of phenylalanine is 1 mg/dl. In affected patients, it is 6 to 80 mg/dl, or greater than 30 mg/dl. The another enzyme tetrahydroxybiopterin improves the function of PAH. If there are defects in THB, hyperphenylalaninemia occurs, which is called as non-classical PKU (Centerwall, & Centerwall, 2000). In the US, all infants are tested for this disease. The affected infants develop symptoms within six months, such as irritability, vomiting, rashes and convulsions. Its most devastating effect is neurological damage . Untreated children show signs of CNS problems such as active tendon reflexes and increased muscle tone. Children may develop mental retardation and convulsions. These effects can be prevented by proper treatment (Centerwall, & Centerwall, 2000).

This disease requires maintenance of its diet, as its increased levels cause decrease in IQ and behavioral disturbances. Precautions should be taken for women with PKU and if they want to become pregnant. To maintain low levels is essential for the fetal growth (Centerwall, & Centerwall, 2000). The fetus can be harmed by the mother's levels of phenylalanine during growth. If the phenylalanine level is not controlled, the baby may have mental retardation or microcephaly. Some of them show low birth weight, cardiac defects, and other facial ...