The thick and sticky mucus can block the tubes that carry air in and out of the lungs, which can cause signs and symptoms of: 3 

• Persistent cough with sputum production

• Wheezing

• Inability or decreased ability to perform physical exercises

• Repeated lung infections

• Inflamed nasal passages and congestion

• Recurrent sinusitis 

Respiratory complications: 3 

• Damaged airways (bronchiectasis)

• Chronic infections

• Growths in the nose (nasal polyps)

• Coughing up blood (hemoptysis)

• Pneumothorax

• Respiratory failure

• Acute exacerbations

The thick and sticky mucus can block tubes that carry digestive enzymes from the pancreas to the small intestines. With low to no production of digestive enzymes, that can lead to: 2, 3 

• Foul-smelling, greasy stools

• Poor weight gain and growth

• Intestinal blockage (particularly in newborns of meconium ileus)

• Chronic or severe constipation

Digestive complications: 2, 3 

• Nutritional deficiencies – Thick mucus can block tubes that carry digestive enzymes from the pancreas to the intestines, which challenges the body to absorb protein, fat or fat-soluble vitamins, and other nutrients.

• Intestinal obstruction

• Distal intestinal obstruction syndrome (DIOS)

• Diabetes – CF can increase the risk of diabetes with ~20% of teenagers and 40-50% of adults with CF developing diabetes

• Liver disease – Tubes that carry bile from the liver and gallbladder to the small intestine may become blocked or inflamed, which increases the risk of liver disease. 

Thickness of the mucus can also affect reproductive health complications: 1, 3 

• Infertility in men – The vas deferens that are connected to the testes and prostate gland can be blocked with mucus or missing entirely. As a result, accounts for 95% infertility rates. 5  However, there are certain fertility treatments and surgical procedures, such as assisted reproductive technology (ART), that can sometimes make it possible for men with CF to become biological fathers.

• Reduced fertility in women – Women with CF may have wall thickening of the cervix with thick mucus, which can lead to irregular ovulations. However, with appropriate guidance from the obstetrician and appropriate contraceptives not being used, women with CF can still be fertile.