Cystic fibrosis (CF)
Cystic fibrosis (CF) - a life-threatening disorder that causes severe lung damage and nutritional deficiencies - used to be a genetic mystery, and most people with the disease didn't live beyond their teens. But researchers have made progress in unraveling the genetic basis of CF, which has led to earlier detection. In addition, improved and more consistent treatments now allow people with CF to live into their 30s and 40s and even beyond, and to have fuller, more comfortable lives.
CF is an inherited (genetic) condition affecting the cells that produce mucus, sweat, saliva and digestive juices. Normally, these secretions are thin and slippery, but in CF, a defective gene causes the secretions to become thick and sticky. Instead of acting as a lubricant, the secretions plug up tubes, ducts and passageways, especially in the pancreas and lungs. Respiratory failure is the most dangerous consequence of CF.
Most babies born with CF are diagnosed by age 3, although mild forms of the disease may not be detected until the third, fourth or fifth decade of life. Although there's still no cure, the emerging field of gene therapy may someday help correct lung problems in people with CF.
Signs and symptoms
The specific signs and symptoms of CF can vary, depending on the severity of the disease. For example, one child with CF may have respiratory problems but not digestive problems, while another child may have both. In addition, the signs and symptoms of CF may vary with age.
In some newborns the first sign may be a blockage of the intestines (meconium ileus). This occurs when meconium — tarry, greenish-black stools normally passed by an infant in the first day or two after birth — becomes so thick it can't move through the intestines. Other signs in newborns may include a failure to grow, bulky and greasy stools (steatorrhea), and frequent respiratory infections.
The signs and symptoms of CF in children and young adults may include:
In CF, a defective gene alters a protein that regulates the normal movement of salt (sodium chloride) in and out of cells. This results in thick, sticky secretions in the respiratory and digestive tracts, as well as in the reproductive system. It also causes increased salt in sweat on the skin.
The affected gene, which is inherited from a child's parents, is known as a recessive gene. This means children need to inherit two copies of the gene, one from each parent, in order to have the disease. If children inherit only one copy, they won't develop CF, but they will be carriers and possibly pass the gene to their own children.
If two people who carry the defective gene conceive a child, there's a 25 percent chance the child will have CF, a 50 percent chance the child will be a carrier of the CF gene, and a 25 percent chance the child will neither have the disease nor be a carrier.
People who carry the CF gene are healthy and have no symptoms. In fact, it's estimated that as many as 10 million people may be carriers of a CF gene and not know it. Although parents often blame themselves when a child is born with CF, it's important to remember that nothing a parent does causes this disease.
In addition, some experts believe that an imbalance of essential fatty acids may play a role in cystic fibrosis. People with CF appear to have excessively high levels of arachidonic acid and a deficiency of another fatty acid, docosahexaenoic acid. Healthy people who carry one CF gene have fatty acid levels midway between those of people with CF and people with no genetic mutations for the disease. But the exact nature of the relationship between fatty acid levels and the gene defect that causes CF isn't clear.
The greatest risk factor for CF is a family history of the disease. If both you and your partner come from families with CF, the chances are one in four that each of your children will also have CF.
Your risk is also greater if you're of Northern European ancestry. In that case, you have a one in 29 chance of carrying the gene.