What causes cystic fibrosis?

People with cystic fibrosis (CF) cannot control the levels of salt and water in their body cells properly, so their body fluids are thicker than usual. They have more salt in their sweat, which doctors can measure to diagnose the condition (the 'sweat test'). In 1989, researchers discovered that people with CF have no working version of a gene that usually makes a protein that controls salt levels.

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DNA analysis of cystic fibrosis. Each lane shows a different person's DNA: the upper band is unaffected (left arrow) and the lower band is affected (right arrow). The parents are unaffected carriers, the child on the right is affected and the child on the left is unaffected.

How is cystic fibrosis inherited?

Cystic fibrosis (CF) affects people who inherit two copies of an altered gene from their carrier parents. Carrier parents have a one-in-four chance of having an affected child, a one-in-two chance of having a child who is an unaffected carrier and a one-in-four chance of having a child who doesn't have the altered gene at all. Carriers of CF are not affected themselves, as they have a working gene as well as an altered one.

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Inheritance of cystic fibrosis.

Screening for cystic fibrosis carriers?

In the UK, about one in 25 people carries the altered gene that causes cystic fibrosis (CF). They are unaffected by the condition, and most will never know they are carriers. But if two carriers have children, each child has a one-in-four chance of inheriting two altered genes and being born with CF. Doctors sometimes offer tests to identify carrier couples, to help them make decisions when planning a pregnancy. But there are many versions (alleles) of the altered gene involved, and tests cannot identify them all.

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Couples who are both carriers of cystic fibrosis are offered genetic counselling.

 

Principal Funder:

Wellcome trust

Major Sponsors:

GlaxoSmithKline life technologies