What is Cystic Fibrosis? Explain the mechanism behind this disease.

Cystic fibrosis (CF) is an autosomal recessive genetic condition most commonly caused by the deltaF508 mutation in the CFTR (Cystic Fibrosis Transmembrane Regulator) gene. This disease is characterised by difficulty breathing, recurrent lung infections and problems with pancreatic function (pancreatic insufficiency).

The CFTR gene encodes an ATP gated plasma membrane chloride channel expressed in the cells lining the sweat gland, lungs, pancreas and other glands in the body. In healthy individuals this chloride channel transports chloride ions out of cells lining these glands into the inside of the gland. This draws water molecules into the gland. In individuals with CF, mutations to CFTR lead to the production of non-functioning channels, or the absence of CFTR channels.

In CF, the absence of these chloride ions leads to a reduction in the amount of water that passes into the gland. The most notable consequence of this is an increased viscosity (thickness) of the mucus produced in the lungs. This thicker mucus is harder for the cilia in the lungs to clear and increases the risk of infection. This is why individuals with CF have recurrent lung infections and difficulties breathing.

Pancreatic issues in CF are the result of blockage of the pancreatic ducts by the thickened mucus, leading to damage by accumulated digestive enzymes.