The thick and sticky mucus associated with cystic fibrosis clogs the tubes that carry air in and out of your lungs. This can cause signs and symptoms such as:
• A persistent cough that produces thick mucus (sputum)
• Wheezing
• Exercise intolerance
• Repeated lung infections
• Inflamed nasal passages or a stuffy nose
• Recurrent sinusitis
Digestive signs:
The thick mucus can also block tubes that carry digestive enzymes from your pancreas to your small intestine. Without these digestive enzymes, your intestines aren't able to completely absorb the nutrients in the food you eat. The result is often:
• Foul-smelling, greasy stools
• Poor weight gain and growth
• Intestinal blockage, particularly in newborns (meconium ileus)
• Chronic or severe constipation, which may include frequent straining while trying to pass stool.
Causes:
The cystic fibrosis transmembrane conductance regulator (CFTR) gene — changes a protein that regulates the movement of salt in and out of cells. The result is thick, sticky mucus in the respiratory, digestive and reproductive systems, as well as increased salt in sweat.
Many different defects can occur in the gene. The type of gene mutation is associated with the severity of the condition.
Children need to inherit one copy of the gene from each parent in order to have the disease. If children inherit only one copy, they won't develop cystic fibrosis.
Courtesy: Mayo Clinic