What is Cystic fibrosis?

Cystic fibrosis is the commonest life limiting inherited disease in the UK. The condition affects the production of mucus in all organs of the body that secrete mucus. Mucus is thicker and stickier than normal. The abnormal mucus primarily affects the function of the lungs, the state of the lungs determine disability and survival in most cases. Respiratory failure due to progressive lung disease is the usual cause of death in cystic fibrosis.

The gut is the second most common organ to be significantly affected. The effects on the gut are life limiting and the second most common cause of disabling effects and care that is required in this condition.

Cystic fibrosis is a recessively inherited genetic condition. Genes consist of two pairs of alleles; one allele is inherited from each parent. A dominant gene is always expressed and a recessive gene is only expressed if both halves of the pair are recessive. A good example is eye colour, brown is dominant and blue is recessive. If both brown and blue eye colour alleles are present the eyes will be brown because brown is dominant. The person will be ‘carrying’ the blue gene.
The gene affected in cystic fibrosis encodes for a protein called Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) that controls the movement of salt across membranes in the body. In the UK about 1 in 25 people carry an abnormal recessive form of this gene. They are not affected by cystic fibrosis because the other dominant gene is expressed. The abnormal trait is expressed only if both copies are abnormal. If 2 carriers have a baby together their child can inherit the faulty copy of the gene from each parent. If the child has two abnormal copies of the gene and no normal copy to compensate, he/she will have cystic fibrosis. Each child of parents who are carriers has a 1 in 4 chance of cystic fibrosis.

Image reproduced with kind permission of the Cystic Fibrosis Trust illustrates this:

What is the incidence and prevalence of cystic fibrosis?

Cystic fibrosis is the commonest life limiting inherited disease in the UK. The incidence is 1 in every 2500 live births, 5 babies are born each week with cystic fibrosis. There are 2 million carriers of the cystic fibrosis gene in the UK and more than 8000 people with cystic fibrosis. 31 people aged 19 and under died of cystic fibrosis in 2008.