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Cystic Fibrosis

Disease Characteristic
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.

List of CF mutaitons tested in this assay
delF508 delI507 G330X R334W R553X  621+1G>T A559T 1717-1G>A 3849+10kbC>T 
W1282X 2184delA G85E  R117H R347P  711+1G>T 3659delC 1898+1G>A  S1255X C>A
R560T  2307insA N1303K R1066C S549N  delF311  3876delA  1812-1G>A  3120+1G>A 
W1089X G542X R1162X A455E  H199Y  1288insTA 296+2T>A   2789+5G>A  2105-2117del13ins 
W1204X G551D  G480C R1158X 3199d6 3791delC 405+3A>C 406-1G>A  S1255X A>G
R75X  935delA Q98R  S492F  P205S  663delT  2055del9>A 3272-26A>G CFTRdele2,3 

Criteria for Genetic Testing

   Presence of any of the CF symptoms in a child

In 1997 and American College of Medical Genetics (ACMG) and American College of Obstetrics and Gynecology (ACOG) recommended prenatal screening for couples in 2001.


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