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Cystic fibrosis: Causes, symptoms, diagnosis, treatment

Cystic fibrosis, sometimes referred to as CF, is an inherited condition causing the lungs and digestive system to get clogged up with sticky, thick mucus. Cystic fibrosis can be life threatening.

The condition affects more than 10,000 people in the UK.

There is no cure for cystic fibrosis, but treatment can help ease symptoms and help prevent complications.

All babies are screened for CF soon after they are born with a tiny amount of blood taken with a heel prick.

CF complications

Reduced oxygen in the blood with CF leads to a characteristic rounding and enlargement of the nail bed in the fingers and toes, called clubbing. Those with the disease may also develop a barrel-shaped chest as a result of their increased work to breathe. Repeated infections often lead to fleshy growths inside the nose, called nasal polyps.

The thick mucus also obstructs the ducts of the pancreas, preventing digestive enzymes from reaching the intestines. So those with CF do not absorb nutrients from their food well, and they eliminate undigested food through the bowel, resulting in very large, smelly stools. Because so little food is absorbed, children with CF have difficulty gaining and maintaining weight, despite a healthy appetite and diet.

CF also affects the reproductive systems of both males and females. Although females with CF have normal fallopian tubes and ovaries, their thick cervical secretions may block sperm entry and prevent them from getting pregnant. Males with CF are almost always infertile because they produce relatively few or no sperm. Abnormally thick secretions may block the ducts that carry sperm, or the ducts may not develop properly.

Another hallmark of CF is an unusually high concentration of sodium and chloride ( salt) in the sweat. The defective CF gene causes faulty chloride movement in CF cells. As a result, parents often report that their babies "taste very salty" when they kiss them.

What causes cystic fibrosis?

Cystic fibrosis occurs in children who have inherited two abnormal copies of a specific gene, one from each parent. A parent who does not have CF but has one normal copy of this gene and one abnormal copy is called a CF carrier. The normal copy dominates, so the parent shows no sign of CF. In some cases, carriers pass on their normal gene to their child. In other instances, they pass on their abnormal copy. A child who receives a normal copy from one parent and an abnormal copy from the other will be a CF carrier and won't have the disease. A child who receives an abnormal gene from both parents will develop CF.

When both parents carry one abnormal copy of the gene, each child they produce has a 25% chance of inheriting two abnormal copies and having the disease, a 25% chance of inheriting two normal copies, and a 50% chance of inheriting one abnormal copy and one normal copy - causing them to be a carrier.

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