Genetics and Evolution: Cystic Fibrosis and Down Syndrome Cystic Fibrosis is a disorder where the exocrine glands secrete abnormally thick mucus, leading to obstruction of the pancreas and chronic infections of the lungs, which usually cause death in childhood or early adulthood. Some mildly affected patients may survive longer. Doctors can diagnose the disease by testing the patients perspiration because people with Cystic Fibrosis have high amounts of salt in their perspiration. Those with respiratory infections are treated with antibiotics, with aerosols that relieve constriction of the airways and liquefy the thick