Cystic fibrosis. Conceptual illustration of DNA (pink) and cell membrane (brown) in cystic fibrosis. Also known as mucoviscidosis, this recessive genetic disorder mainly affects the lungs. It causes frequent infections and thick mucus in the airways, but also affects the pancreas, liver, kidneys, and intestine. It is caused by maternal and paternal mutations (red) in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CFTR (green) is a chloride ion channel found in cell membranes. It is involved in production of digestive fluids, sweat and mucus. Chloride ions are coloured white. Defective CFTR proteins lead to disruption of epithelial fluid transport in the lungs and elsewhere, resulting in thickened mucus and repeated bacterial infection, amongst other symptoms.