Cystic fibrosis is a disease that causes mucus to build up in the body. People with cystic fibrosis produce thicker and stickier mucus because their mucus contains less water. This occurs because cystic fibrosis interrupts the flow of both water and salt molecules out of the cells that produce mucus. Because the resulting mucus is so dense and sticky, it builds up in organs, particularly the lungs and pancreas. This presents significant respiratory and digestive problems.
