Cystic Fibrosis

Cystic fibrosis is caused by a genetic mutation on chromosome 7 of the genome. A particular part of this chromosome is responsible for making the cystic fibrosis transmembrane conductance regulator (CFTR) and was discovered in 1989. This mutation affects how the cystic fibrosis CFTR functions. There are a number of different ways this can happen and is based on the genotype (see ‘what are genotypes’). The CFTR is found on epithelial cells all over the body. The CFTR is involved in letting chloride and sodium (the compounds that make salt) into and out of the cell. In the lung this malfunction disrupts the airway surface layer (ASL).

The ASL is a layer of fluid that lines the lungs. In healthy children there are cilia that are attached to the epithelial cells that rest in this layer. In this layer the cilia are able to ‘beat’ and move things like mucus up and out of the lungs. In CF there is no ASL (or it is very thin). This means the cilia can’t do their normal function. Mucus then builds up in lungs. The mucus provides a great place for bacteria to grow. If a child gets an infection the bacteria grows in the mucus of the lungs. Bacteria and viruses are around us all the time. Other people carry them and they are in the environment (in food, the soil, drains etc). Once a child gets an infection the bacteria and the body's immune response attack the lung and cause lung damage.