Causes of cystic fibrosis
Cystic fibrosis is a genetic inherited disease
Our bodies are made up of cells, and each cell contains around 20,000–25,000 genes.
Genes also contain the instructions for making proteins, which are the building blocks for everything in the body and are very important for keeping our bodies working properly.
Sometimes, a gene might have a change in it that causes it to behave differently to a normal gene. This change is called a mutation.
Cystic fibrosis (CF) is a disease people are born with. It is a genetic disease, meaning it is inherited from your parents.
- One of the genes in our bodies is called the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Everyone inherits two copies of this gene, which contains the instructions for making the CFTR protein.
- If one of the CFTR genes you inherit has a mutation (change) that causes cystic fibrosis, this means you are a “carrier” of the mutated gene, but you do not have CF.
- If both of the CFTR genes you inherit have a mutation that causes cystic fibrosis, you are born with CF.
There are many different types of CFTR gene mutations
- Not everyone with CF has the same mutations (changes) in their CFTR genes. We know of over 2,000 different CFTR gene mutations.
5At least 352 of these cause CF 6, but most of them are extremely rare. 7
- People with CF can either have two copies of the same CF gene mutation (homozygous), or two different CF gene mutations (heterozygous).
- F508del is the most common CFTR gene mutation.
791.7% of people living with CF in Ireland in 2019 had at least one copy of the F508del mutation. 8 Other common mutations in Ireland include the G551D mutation (15.3%) and the R117H mutation (6.4%). All other CFTR mutations affect less than 4% of the Irish CF population. 8
Knowing your CF genotype
The type of CFTR gene mutations you have is called your ‘genotype’, and this is something your doctor should know and be able to tell you.
NIH Genetics Home Reference. What is a cell? Available at: https://ghr.nlm.nih.gov/primer/basics/cell. Last accessed April 2021.
NIH Genetics Home Reference. What is a gene? Available at: https://ghr.nlm.nih.gov/primer/basics/gene. Last accessed April 2021.
Orenstein DM. Cystic Fibrosis: A Guide for Patient and Family. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
NIH Genetics Home Reference. What is a gene mutation and how do mutations occur? Available at: https://ghr.nlm.nih.gov/primer/basics/cell Last accessed April 2021.
The Clinical and Functional Translation of CFTR (CFTR2) resources. How is CF inherited. Available at: https://cftr2.org/resources. Last accessed April 2021.
CFTR2. CFTR2 Variant List History. 10 January 2020. Available at: https://cftr2.org/mutations_history. Last accessed April 2021.
Castellani C, et al. J Cyst Fibros 2008; 7(3): 179 ̶ 196.
Cystic Fibrosis Registry of Ireland. 2019 Annual Report. Available at: https://www.cfireland.ie/images/uploads/resources/cfri.ie-2_.pdf. Last accessed April 2021.