Most of the symptoms of cystic fibrosis (CF) are caused by the thick, sticky mucus. The most common symptoms include: 1  Frequent coughing that brings up thick sputum, or phlegm (flem). 2  Frequent bouts of bronchitis and pneumonia. 3  They can lead to inflammation and permanent lung damage.4  Salty-tasting skin.5  Dehydration. 6  Infertility (mostly in men).he most common symptoms include: 1  Frequent coughing that brings up thick sputum, or phlegm (flem). 2  Frequent bouts of bronchitis and pneumonia. 3  They can lead to inflammation and permanent lung damage. 4  Salty-tasting skin. 5  Dehydration. 6  Infertility (mostly in men).