Cystic fibrosis is an inherited chronic disease that affects the lungs and digestive system of about 30,000 children and adults in the United States (70,000 worldwide). A defective gene and its protein product cause the body to produce unusually thick, sticky mucus.
How Common are CF Mutations?
* About 1,000 new cases of cystic fibrosis are diagnosed each year.
* More than 70% of patients are diagnosed by age two.
* More than 40% of the CF patient population is age 18 or older.
* In 2006, the predicted median age of survival was 37 years.
To date more than 1200 mutations have been identified in the CFTR gene with varying frequencies depending on race and ethnicity.
Genes and Mutations (Genotype-Phenotype Relationships)
The gene responsible for CF, CFTR (CF transmembrane conductance regulator) was identified in 1989. It is located on the long arm of the chromosome 7 and is approximately 250,000 base pairs long with 27 exons coding for a 1480 amino acid long protein.
Mutations and populations
Over 100 mutations in the CFTR gene have shown to have frequencies of greater than 0.001 (1 in 1000) among North Americans with the most common being the DeltaF508 which accounts for 70% of all CF cases in the Caucasian population. The less common ones include: G542X (2.4%), G551D (1.6%), N1303K (1.3%), W1282X (1.2%).
Phenotypes and Symptoms
* very salty-tasting skin;
* persistent coughing, at times with phlegm;
* frequent lung infections;
* wheezing or shortness of breath;
* poor growth/weight gain in spite of a good appetite; and
* frequent greasy, bulky stools or difficulty in bowel movements.
We test for the ACOG recommended 25 mutation panel as well as California expanded 45+9 panel. All tested mutations are listed in the table below.
Criteria for Genetic Testing
Presence of any of the CF symptoms in a child