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Cystic Fibrosis Causes

Cystic fibrosis is a hereditary, or genetic, disease. It is most common in Caucasian-American children, occurring in about one in every 2,000 births. It is less common among African-American children, (about one in 17,000 births), and even more rare among Asian Americans (one in 100,000 births).

The mode of inheritance is autosomal, which means that it does not involve the x or y chromosomes, which determine sex. It is also recessive, which means that the disease is inherited from both parents. About five percent of Caucasian Americans (one in 28) are believed to carry the gene. Carriers do not have symptoms of the disease, and often do not even realize that they are one of more than 10 million people who carry cystic fibrosis. The number of cystic fibrosis carriers is likely to increase in the future.

This chart can help you determine the genetic probability of having a child with cystic fibrosis.

Parents Chance of
Unaffected Child
Chance of
Child Carrier
Chance of
Child with CF
Unaffected + Carrier 50% 50% No Chance
Two Carriers 25% 50% 25%
Unaffected + CF Patient No Chance 100% No Chance
Carrier + CF Patient No Chance 50% 50%
2024 American Association for Respiratory Care