What Causes Cystic Fibrosis?

What Is Cystic Fibrosis?

Cystic fibrosis (CF) is a hereditary disease of the secretory glands, which produce sweat and mucous. CF affects mainly the pancreas, lungs, liver, sex organs and sinuses. In CF, particular glands create abnormal secretions. Some people with mild forms of CF may not have any symptoms until they reach their teen years or become young adults. On the other hand, people with severe cases may have serious digestive and lung problems all their lives. The severity of CF depends on the degree of defect of the CFTR gene.

The CFTR Gene

The disease is caused by a gene defect involving the CFTR gene (cystic fibrosis transmembrane regulator). A child who inherits an abnormal CFTR gene from both parents has CF. However, a child inheriting an abnormal CFTR gene from one parent and a normal gene from the other won't have CF, although he will be a carrier for CF.

Function of the CFTR Gene

The CFTR protein serves as a channel across cell membranes producing mucous, sweat, tears, saliva and digestive enzymes, carrying negatively-charged chloride ions in and out of cells. This helps control water moving in tissues, which is essential for producing thin mucous that flows freely. Mucus is the substance that lubricates as well as protects the linings of the digestive system, reproductive system, airways and other tissues and organs. The CFTR protein controls how other channels work, including those moving sodium ions (that are positively charged) across cell membranes. These channels are vital in the normal functioning of organs such as the pancreas and lungs.

Lung Problems from CF

When the CFTR gene is working correctly, it produces a protein controlling moving water and salt as it flows in and out of the cell's body. However, the CFTR gene doesn't function properly in people who have CF. This malfunction results in sticky mucous and salty sweat accumulating in the lungs. As mucous continues to collect, it blocks airways, which are the tubes carrying air in and out of the lungs. This mucous buildup creates a breeding ground for bacteria to grow, leading to serious lung infections that can severely injure the lungs over time.

Pancreas Problems

Mucous can also block the ducts or tubes to the pancreas. While the respiratory system glands produce thick, dry secretions, the pancreas produces a sticky, thick mucous. This obstructs the enzymes from the pancreas on their way to the small intestine. Enzymes from the pancreas help break down food, making it possible to absorb proteins and fats. When enzymes can't do their job, food nutrients leave the body without being used, which can result in intestinal gas as well as bulky stools, constipation and pain.

Resources

• What Causes Cystic Fibrosis
• CFTR Gene
• Cystic Fibrosis