Mutation Frequencyworldwide ΔF508 66%–70% G542X 2.4% G551D 1.6% N1303K 1.3% W1282X 1.2% All others 27.5% Cystic fibrosis is the most common life-limiting autosomal recessive disease among people of European heritage. In the United States, about 30,000 individuals have CF; most are diagnosed by six months of age. In Canada, about 4,000 people have CF. Around 1 in 25 people of European descent, and one in 30 of white Americans, is a carrier of a CF mutation. Although CF is less common in these groups, roughly one in 46 Hispanics, one in 65 Africans, and one in 90 Asians carry at least one abnormal CFTR gene. Ireland has the world's highest prevalence of CF, at one in 1353. Although technically a rare disease, CF is ranked as one of the most widespread life-shortening genetic diseases. It is most common among nations in the Western world. An exception is Finland, where only one in 80 people carries a CF mutation. The World Health Organization states, "In the European Union, one in 2000–3000 newborns is found to be affected by CF". In the United States, one in 3,500 children is born with CF. In 1997, about one in 3,300 white children in the United States was born with CF. In contrast, only one in 15,000 African American children suffered from it, and in Asian Americans, the rate was even lower at one in 32,000. Cystic fibrosis is diagnosed equally in males and females. For reasons that remain unclear, data have shown that males tend to have a longer life expectancy than females, though recent studies suggest this gender gap may no longer exist, perhaps due to improvements in health care facilities. A recent study from Ireland identified a link between the female hormone estrogen and worse outcomes in CF. The distribution of CF alleles varies among populations. The frequency of ΔF508 carriers has been estimated at one in 200 in northern Sweden, one in 143 in Lithuanians, and one in 38 in Denmark. No ΔF508 carriers were found among 171 Finns and 151 Saami people. ΔF508 does occur in Finland, but it is a minority allele there. CF is known to occur in only 20 families (pedigrees) in Finland. Evolution The ΔF508 mutation is estimated to be up to 52,000 years old. Numerous hypotheses have been advanced as to why such a lethal mutation has persisted and spread in the human population. Other common autosomal recessive diseases such as sickle-cell anemia have been found to protect carriers from other diseases, an evolutionary trade-off known as heterozygote advantage. Resistance to the following have all been proposed as possible sources of heterozygote advantage: * Cholera: With the discovery that cholera toxin requires normal host CFTR proteins to function properly, it was hypothesized that carriers of mutant CFTR genes benefited from resistance to cholera and other causes of diarrhea. Further studies have not confirmed this hypothesis. * Typhoid: Normal CFTR proteins are also essential for the entry of Salmonella Typhi into cells, suggesting that carriers of mutant CFTR genes might be resistant to typhoid fever. No in vivo study has yet confirmed this. In both cases, the low level of cystic fibrosis outside of Europe, in places where both cholera and typhoid fever are endemic, is not immediately explicable. * Diarrhea: The prevalence of CF in Europe might be connected with the development of cattle domestication. In this hypothesis, carriers of a single mutant CFTR had some protection from diarrhea caused by lactose intolerance, before the mutations that created lactose tolerance appeared. * Tuberculosis: Another possible explanation is that carriers of the gene could have some resistance to tuberculosis. This hypothesis is based on the thesis that CFTR gene mutation carriers have insufficient action in one of their enzymes – arylsulphatase - which is necessary for Mycobacterium tuberculosis virulence. As M. tuberculosis would use its host's sources to affect the individual, and due to the lack of enzyme it could not presents its virulence, being a carrier of CFTR mutation could provide resistance against tuberculosis.
medical cause of Bronchiectasis
medical cause of Bronchiolitis
medical cause of Hemoptysis
medical cause of Acute bronchitis
symptom of Idiopathic pulmonary fibrosis
symptom of Bronchiectasis
complications of Bronchiolitis
medical cause of Bronchiolitis obliterans