Definition of Cystic fibrosis:

Cystic fibrosis is an inherited disease that causes thick, sticky mucus to build up in the lungs and digestive tract. It is one of the most common type of chronic lung disease in children and young adults, and may result in early death.

Causes, incidence, and risk factors:

Cystic fibrosis (CF) is caused by a defective gene which tells the body to produce abnormally thick and sticky fluid, called mucus. This mucus builds up in the breathing passages of the lungs and the pancreas, the organ that helps to break down and absorb food.

This collection of sticky mucus results in life-threatening lung infections and serious digestion problems. The disease may also affect the sweat glands and a man's reproductive system.

Millions of Americans carry the defective CF gene, but do not have any symptoms. That's because a person with CF must inherit two defective CF genes -- one from each parent. An estimated 1 in 29 Caucasian Americans have the CF gene. The disease is the most common, deadly, inherited disorder affecting Caucasians in the United States. It's more common among those of Northern or Central European descent.

Most children with CF are diagnosed by age 2. A small number, however, are not diagnosed until age 18 or older. These patients usually have a milder form of the disease.