This is the most common serious genetic disease in Caucasian children, with an incidence of about one per 2,500 births, and more than 6,000 patients in the UK (30,000 in the USA). It is an autosomal recessive disorder of the mucus-secreting glands of the lungs, the pancreas, the mouth, and the gastrointestinal tract, as well as the sweat glands of the skin. The defective gene is sited on chromosome 7 which encodes for a protein, cystic ﬁbrosis transmembrane conductance regulator (CFTR). Individuals who inherit the gene only on one set of chromosomes can, however, carry the defect into successive generations. Where parents have a child with cystic ﬁbrosis, they have a one-infour chance of subsequent children having the disease. They should seek GENETIC COUNSELLING.
The disorder is characterised by failure to gain weight in spite of a good appetite, by repeated attacks of bronchitis (with BRONCHIECTASIS developing at a young age), and by the passage of loose, foul-smelling and slimy stools (faeces). AMNIOCENTESIS, which yields amniotic ﬂuid along with cells shed from the fetus’s skin, can be used to diagnose cystic ﬁbrosis prenatally. The levels of various enzymes can be measured in the ﬂuid and are abnormal when the fetus is aﬀected by cystic ﬁbrosis. Neonatal screening is possible using a test on blood spots – immunoreactive trypsin (IRT).
In children with symptoms or a positive family history, the disease can be tested for by measuring sweat chloride and sodium. This detects the abnormal amount of salt that is excreted via the sweat glands when cystic ﬁbrosis is present. Conﬁrmation is by genetic testing.
Treatment This consists basically of regular physiotherapy and postural drainage, antibiotics and the taking of pancreatic enzyme tablets and vitamins. Some children need STEROID treatment and all require nutritional support. The earlier treatment is started, the better the results. Whereas two decades ago, only 12 per cent of aﬀected children survived beyond adolescence, today 75 per cent survive into adult life, and an increasing number are surviving into their 40s. Patients with end-stage disease can be treated by heart-lung transplantation (with their own heart going to another recipient). Research is underway on the possible use of GENE THERAPY to control the disorder. Parents of children with cystic ﬁbrosis, seeking help and advice, can obtain this from the Cystic Fibrosis Trust.