Cystic Fibrosis - Symptoms - CFTR mutation - Diagnosis - Treatment - Prognosis

Research has proven that a mutation in the CFTR (cystic fibrosis trans-membrane regulator) gene causes cystic fibrosis. This gene produces a protein that controls the transport of chloride ions and water across the cellular membranes. Hence the name CFTR gene / protein.

CFTR protein is found to be present in cells lining the organs such as lungs, pancreas, colon and the uro-genital tract. In CF-affected individuals, the aberrant gene in turn makes a faulty protein whose function is impaired. This results in –

• The improper movement of ions and salt across the cell membranes, causing salty sweat.

• Formation of excessive amount of thick, sticky mucus.

Scientists assert that the CFTR protein affects other body functions too which explains the other symptoms and complications associated with CF.

The CFTR gene is known to be impaired in several different ways in the affected persons and the type of defect is known to influence the severity of the disease in a person. The most common error is the loss of 3 base pairs from the CFTR gene resulting in the loss of an amino acid, phenylalanine, in the protein formed. However, this type of mutation accounts for only 70-80% of CF cases.

Other genes have also been discovered that play a role in disease progression.

Every parent contributes to the two CFTR genes in a person. Any child who inherits a faulty CFTR gene from both the parents will develop cystic fibrosis. If a child inherits one normal gene and another faulty gene will be a ‘carrier’ of the disease who will not suffer from any of its symptoms but who carry the potential to pass it on to his children.

If one parent has normal CFTR genes and another is a ‘carrier’ then each child born has a -

• 50% chance of being normal, and

• 50% chance of being a carrier

If both parents are ‘carriers’ the following is the hereditary pattern. Each child has a -

• 25 % chance of inheriting two normal CFTR genes (normal)

• 50 % chance of inheriting one normal CFTR gene and one faulty CFTR genes (carriers)

• 25 % chance of inheriting two faulty CFTR genes (cystic fibrosis)