Cystic Fibrosis: General information
Cystic fibrosis (CF) is the most common genetic disease in Caucasians. Carriers are estimated to be 4-5% of the general population and the birth rate of children affected by the disease is approximately 1:2000-1:2500 live births.
It is a genetic disease that follows autosomal recessive mode of inheritance; both parents have to be carriers of the disease and their children have 25% chance to be affected by cystic fibrosis.
The genetic variability is very high, more than 1900 different mutations in the responsible gene (Cystic Fibrosis Transmembrane Regulator) have been described worldwide. The mutations and their respective frequencies have a distinct ethnic and geographic distribution.
The most frequent mutation in CFTR gene is p.F508del, with a frequency ranging from 70-80% in northern European countries to 30-54% in southern European countries.
Cystic Fibrosis: Clinical manifestations & symptoms
The most severely affected systems are the respiratory, digestive and reproductive system as well as the sweat glands.
Atypical forms of the disease include male infertility due to congenital absence of the vas deference (CBAVD), chronic pancreatitis, some forms of bronchiectasis and chronic idiopathic pulmonary diseases.
Cystic Fibrosis & Prevention: Indications for testing
The best way to prevent the birth of affected children is to detect the carriers of cystic fibrosis in the general population and perform appropriate prenatal genetic diagnosis.
There is no biochemical of hematological marker available for the screening of carriers, therefore the molecular analysis of CFTR gene is the only way to detect potential carriers of the disease.
Due to the high frequency of the carriers of the disease, screening should be offered to all the couples that plan to start a family, before or during the first stages of the pregnancy. The most appropriate and safe method is to perform the complete CFTR gene analysis to one of the partners.
The molecular analysis for cystic fibrosis should also be offered to high risk groups, such as members of families with at least one affected member, embryos with echogenic bowel, partners of cystic fibrosis carriers of patients and man with CBAVD. The mutation detection rate in these individuals ranges from 30-70%.
When a parent is a carrier of a cystic fibrosis mutation, there is a 50% chance that his child could inherit the mutation, or inherit the normal CFTR gene.
When both parents are carriers, there is a 25% chance that they will have a child that has inherited both mutations and will thus be affected by cystic fibrosis. The 25% risk of having an affected offspring is the same for every pregnancy, irrespective of the child’s gender. There is also a 50% chance that their child will inherit only one mutation (carrier of cystic fibrosis) and a 25% chance that will not inherit any of the mutations of his parents.
The remaining risk for the birth of an affected child, in the case that one partner is a cystic fibrosis carrier and the other one has done the complete genetic analysis for the mutations in CFTR gene, is 1/2300 (0.004%).
Cystic Fibrosis & Molecular Diagnosis
We recommend that the molecular analysis of cystic fibrosis should include the complete gene sequencing and detection of large genomic rearrangements (deletions & duplications) of CFTR gene.
Our laboratory offers 4 levels of cystic fibrosis screening: