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.
7Approximately 85% of people with CF in Ireland have at least one copy of the F508del mutation. 8
The next most common mutations, for example, G551D, R117H, G542X, 621+1G->T, and N1303K, have a much lower prevalence. 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.
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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 July 2020.
The Clinical and Functional Translation of CFTR (CFTR2) resources. How is CF inherited. Available at: https://cftr2.org/resources. Last accessed July 2020.
CFTR2. CFTR2 Variant List History. 10 January 2020. Available at: https://cftr2.org/mutations_history. Last accessed July 2020.
Castellani C, et al. J Cyst Fibros 2008; 7(3): 179 ̶ 196.
Cystic Fibrosis Trust. UK Cystic Fibrosis Registry. Annual Data Report 2018. Published August 2019.