Phenylketonuria: practical dietary management.

Phenylketonuria (PKU) is an autosomal recessively inherited disorder which prevents the normal metabolism of protein foods. Phenylalanine builds up in the blood and if untreated will cause mental retardation. PKU is treatable by a low-phenylalanine diet for life. The prognosis is good provided the condition is diagnosed within the first two weeks of life and dietary treatment started promptly. Special low-phenylalanine formulae and foods are available on prescription in the UK. Supervision by a dietitian and regular monitoring of phenylalanine levels in the blood are essential. The health visitor and school nurse have an important part to play during the school years in supporting the family. Midwives also play an important part in ensuring that women with PKU adhere to a strict low-phenylalanine diet around the time of conception and during pregnancy. They also take blood samples from all newborn babies to be tested for PKU.