Cystic fibrosis affects the mucus and sweat glands of the body and is caused by a defective gene. Thick mucus is formed in the breathing passages of the lungs and this predisposes the person to chronic lung infections.

Many pancreatic enzymes involved in the breakdown and absorption of fats in the intestine are absent, causing malabsorption (inadequate absorption of nutrients from the intestinal tract) and malnutrition.

Most males with cystic fibrosis are infertile. About one in 2500 Caucasians is affected, and 2-5% of Caucasians carry the cystic fibrosis gene.

It is the most common fatal hereditary disorder affecting Caucasians in the United States. It is most common among Caucasians of Northern or Central European descent and is much less common in other ethnic groups. Risk factors include a family history of cystic fibrosis or unexplained infant death.