Cystic fibrosis (CF) is a disease that affects the mucus and sweat glands. The disease is inherited and mainly affects the lungs, liver, pancreas, sinuses, intestines, and sex organs. In a person with cystic fibrosis, an abnormal gene -- called the cystic fibrosis transmembrane conductance regulator (CFTR) gene -- causes mucus to become thick and sticky. As a result of cystic fibrosis, the stools become bulky; it may not be possible to get enough vitamins A, D, E, and K; and nutrients leave the body unused, which can cause malnourishment. Treatment options for this condition include antibiotics, exercise, and chest physical therapy, among other things.