Cystic fibrosis, CF, or mucoviscidosis, hereditary disease, usually appearing in early childhood, characterized by an abnormality of the exocrine or mucus-screting glands. An excess of thick, sticky mucus accumulates particularly in the lungs and the pancreas, seriously affecting breathing and the digestion of food. CF patients may be identified by large amounts of salt in their perspiration. As the disease progresses the mucus-secreting glands are replaced by fibroid tissue and cysts. Individuals who are carriers of the CF trait are not afflicted with the disease, although the offspring of 2 carriers may inherit the disease. The control of pulmonary infection is critical to survival in CF patients; antibiotics are routinely used to prevent or treat respiratory infections, and physical therapy and the use of certain inhalants are encouraged to help remove the accumulation of mucus in the lungs.