Cystic Fibrosis (CF) is when a gene in the body has mutated, and it can no longer control the fluids and salts that go in and out of the cells. This gene is called Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), and it controls the cells that make sweat and other digestive fluids. If this gene begins to malfunction, instead of a nice flow of fluid, there is a build up of sticky glue like mucus which blocks important ducts and tubes in the body. This makes limbs stiff and difficult to move. If the mucus begins to build in your airways breathing will become difficult and lead to further complications. CF causes problems in the pancreas, liver, bladder, and kidneys, small and large intestine and the reproductive organs. This disease is a very severe condition, which requires daily care and treatment.
Genes inherited from your parent's cause CF. However, you have to inherit one from each of them for the disease to be active. If you only have one mutated copy of the gene, you will not have any symptoms, even though you could be the carrier of the disease.