Parents sometimes spot cystic fibrosis by tasting salt when kissing their child
Children with cystic fibrosis lose so much salt in their sweat that parents may see crystals on the skin or notice a salty taste on a kiss. The standard diagnostic test measures exactly that: chloride in sweat. Behind it lies one faulty protein that turns the body's thin secretions thick and sticky.
Cystic fibrosis is inherited in a recessive pattern: a person must carry faulty copies of the CFTR gene from both parents. Someone with one working copy is a carrier and generally healthy. The CFTR protein moves chloride across cell membranes and helps make sweat, digestive juices and mucus. When it fails, those fluids thicken, clogging the lungs, pancreas, liver and gut.
The lungs bear the heaviest burden. Sticky mucus defeats the airway's normal cleaning system, inviting chronic infection with bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus, and repeated inflammation slowly damages the airways. Cardiorespiratory problems cause about 30 percent of deaths at US treatment centres. In the digestive system, blocked pancreatic ducts stop enzymes from reaching the intestine; most patients, 85 to 90 percent, cannot make enough digestive enzymes, which leads to greasy stools and poor growth. Around 15 to 20 percent of affected newborns have their intestine blocked at birth, and damage to insulin-making cells produces a distinct form of diabetes. The disease is named for the cysts and scarring it causes in the pancreas.
It is most common in people of Northern European descent, affecting about 1 in 3,000 newborns, with roughly 1 in 25 carrying a faulty copy; it is rarest in Africa and Asia. Dorothy Andersen identified it as a distinct disease in 1938, though descriptions matching it go back at least to 1595.
There is still no cure, but outlook has changed dramatically. Oral CFTR modulators, which act on the defective protein itself, have greatly improved survival for people with eligible gene variants who can get them. Estimated median survival now stands at about 65 years in Canada, the United States and the United Kingdom. The European Cystic Fibrosis Society warns that these gains have opened a widening gap with low- and middle-income countries, where screening, testing and standard therapies are often missing.
Source: Cystic fibrosis
