Cystic Fibrosis: CFTR Gene Deletion/Duplication

Condition Description

Cystic Fibrosis (CF) is a chronic genetic condition involving multiple organ systems [1]. Classical CF primarily involves the respiratory and digestive systems, and may have a range of clinical severity. Pulmonary symptoms often include lower airway inflammation, chronic cough, chronic sinusitis, and recurrent infections. Digestive symptoms often include meconium ileus, pancreatic insufficiency resulting in malabsorption and/or failure to thrive, diabetes mellitus, and hepatobiliary disease. Congenital bilateral absence of the vas deferens (CBAVD) is seen in men without pulmonary or digestive symptoms of CF, and results in azoospermia [2]. CBAVD is a significant cause of male infertility.

CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Individuals with mutations in the CFTR gene may also present with milder or atypical symptoms such as pancreatitis or chronic sinusitis.

The incidence of CF is approximately 1 in 3200 live births among Caucasians and is inherited in an autosomal recessive pattern. The carrier frequency is estimated to be approximately 1 in 22-28 in the Caucasian population, 1 in 29 in the Ashkenazi Jewish population, 1 in 60-65 in the African American population, 1 in 46 in the Hispanic population and 1 in 90 in the Asian population.

Initial evaluation and screening of patients for CFTR mutations is accomplished through a panel of 23 common mutations as recommended by the American College of Medical Genetics Subcommittee on Cystic Fibrosis [3] and American College of Obstetrics and Gynecologists [4]. The detection rate of this panel depends on the patients ethnicity (refer to the Cystic Fibrosis Common Mutation Panel).

When the common mutation panel is negative and mutations to the CFTR gene are suspected, sequencing of the entire gene is recommended to detect more rare mutations. Gene sequence analysis is available to test for mutations in the CFTR gene (JK).

Click here for the GeneReviews summary on this condition.

Visit www.ThinkGenetic.com for patient-friendly information on cystic fibrosis.

References:
1. Moskowitz et al. CFTR-related disorders (2005). www.genetests.org
2. Xu et al. Cystic fibrosis transmembrane conductance regulator is vital to sperm fertilizing capacity and male fertility (2007). PNAS 104(23):9816-21.
3. Watson, M. et al. Cystic Fibrosis population carrier screening: 2004 revision of the American College of Medical Genetics mutation panel (2004). Genet Med 6(5):387-91.
4. ACOG Committee Opinion. Update on Carrier Screening for Cystic Fibrosis (2005). Obstetr Gynecol 106:1465-8.
5. Heim et al. Improved detection of cystic fibrosis mutations in the heterogeneous U.S. population using an expanded, pan-ethnic mutation panel (2001). Genet Med 3(3):168-76.
6. Strom et al. (2003) Extensive sequencing of the cystic fibrosis transmembrane regulator gene: assay validation and unexpected benefits of developing a comprehensive test. Genet Med 5(1):9-14.
7. Chevalier-Porst (2005) Identification and Characterization of Three Large Deletions and a Deletion/Polymorphism in the CFTR Gene. Hum Mut Mutation in Brief #806 Online
8. http://www.genet.sickkids.on.ca/

Genes (1)

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Indications

Testing is indicated for:

  • Patients suspected to have a mutation to the CFTR gene and who tested negative for mutation by the common mutation panel.
  • Family members of an affected individual at risk to be carriers of CF.

Methodology

DNA isolated from peripheral blood is hybridized to a CGH array to detect deletions and duplications. The targeted CGH array has overlapping probes which cover the entire genomic region.

Detection

Detection is limited to duplications and deletions. Array CGH will not detect point mutations or intronic mutations. Results of molecular analysis must be interpreted in the context of the patient\'s clinical phenotype.

Specimen Requirements

When sample fails to meet the acceptable criteria, please call 470.378.2200 and ask to speak with a laboratory genetic counselor (eglgc@egl-eurofins.com).
Submit only 1 of the following specimen types
DNA, Isolated
DNA

Requirements
Microtainer
3µg
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Collection and Shipping
Refrigerate until time of shipment in 100 ng/µL in TE buffer. Ship sample at room temperature with overnight delivery.
Whole Blood (EDTA)
WBP

Requirements
EDTA (Purple Top)
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Collection and Shipping
Ship sample at room temperature for receipt at EGL within 24 hours of collection. Do not refrigerate or freeze.

Special Instructions

Completion of the cystic fibrosis common mutation panel should be completed PRIOR to CFTR gene sequence analysis.

  • CF common mutation panel (CF).
  • Ashkenazi Jewish Carrier Panel is available to screen for the panel of 9 autosomal recessive conditions common in individuals of Ashkenazi Jewish background
  • Custom diagnostic mutation analysis (KM) is available to family members if mutations are identified by sequencing.
  • Prenatal testing is available for known familial mutations only. Please call the Laboratory Genetic Counselor before collecting a fetal sample.

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