VOL: 101, ISSUE: 38, PAGE NO: 31
WHAT IS IT?
WHAT IS IT?
- Phenylketonuria (PKU) is a genetic disorder characterised by an inability to utilise the amino acid phenylalanine. - In classic PKU the enzyme phenylalanine hydroxylase is completely or nearly completely deficient so phenylalanine builds up in the blood and tissues. - Classical PKU is inherited in a strictly autosomal recessive manner. This means that two genes for the disorder - one from each parent - must be inherited. - If not treated from soon after birth it affects development and causes severe mental retardation. INCIDENCE
- About 1 in 10,000 births (1 in 4,500 in Northern Ireland). - It is the most common inborn error of protein metabolism. - It is equally frequent in males and females. SCREENING
- Early diagnosis of phenylketonuria (PKU), is important because it is treatable by dietary means. - All newborns in the UK are screened. Phenylalanine levels are measured in a heel-prick blood test. MANAGEMENT
- Treatment is by restricting intake of phenylalanine using a low-protein diet. This is very effective at lowering levels of phenylalanine in the body and allows normal growth and development of the child. - Any high-protein foods such as meat, cheese, poultry, eggs and milk are not permitted. - The diet is supplemented with artificial protein containing no phenylalanine. - In the UK the provision of services for the treatment of phenylketonuria varies widely, from centralised clinics and specialist teams to patient management by a local family practitioner working in isolation. - Medical follow-up is required for periodic development screening and early recognition and intervention for problems. - Dietary restrictions should continue throughout a child’s developing years, and it is thought that some control over phenylalanine intake is necessary for healthy adult life. FAMILY PLANNING
- Appropriate sex education, family planning advice and counselling are important. - Women with PKU who are of childbearing age should closely adhere to the low-phenylalanine diet and monitor phenylalanine levels before conception and throughout pregnancy. - The risk of spontaneous abortion, mental retardation, microcephaly and/or congenital heart disease in the child is high if maternal blood phenylalanine levels are poorly controlled. IMPLICATIONS FOR PRACTICE
- All nurses who work with individuals with PKU should be aware of the dietary requirements and restrictions. - Some medicines contain phenylalanine as a sweetener and should be avoided. - Living with dietary restrictions can be very difficult for children. They may wish to share concerns or feelings about being ‘different’ from peers. - If there is insufficient intake of phenylalanine, which is an essential amino acid, levels may to be too low for growth and body functions, so routine screening is especially important. SUPPORT ORGANISATION
- The National Society for Phenylketonuria was founded in 1973. - It promotes the care and treatment for people with PKU and publishes a wide range of materials including food lists for parents, patients and health care professionals. National Society for Phenylketonuria (2005)What is the National Society for Phenylketonuria (NSPKU)? www.nspku.orgOnline Mendelian Inheritance in Man (2005)Phenylketonuria. www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?cmd=entry&id= 261600.