Editing Asthma (section)

===Genetic===
{| class="wikitable" style = "float: right; margin-left:15px; text-align:center"
|+ CD14-endotoxin interaction based on CD14 SNP C-159T<ref name=Martinez_CD14 />
|-
! Endotoxin levels !! CC genotype !! TT genotype
|-
! High exposure
| Low risk || High risk
|-
! Low exposure
|High risk || Low risk
|}

Family history is a risk factor for asthma, with many different genes being implicated.<ref name=El2010>{{cite book| vauthors = Elward G, Douglas KS |title=Asthma|year=2010|publisher=Manson Pub.|location=London|isbn=978-1-84076-513-7|pages=27–29|url=https://books.google.com/books?id=gS4BsugTBvoC&pg=PA27|url-status=live|archive-url=https://web.archive.org/web/20160517002458/https://books.google.com/books?id=gS4BsugTBvoC&pg=PA27|archive-date=May 17, 2016}}</ref> If one identical twin is affected, the probability of the other having the disease is approximately 25%.<ref name=El2010/> By the end of 2005, 25 genes had been associated with asthma in six or more separate populations, including [[Glutathione S-transferase Mu 1|GSTM1]], [[Interleukin 10|IL10]], [[CTLA-4]], [[SPINK5]], [[Leukotriene C4 synthase|LTC4S]], [[Interleukin-4 receptor|IL4R]] and [[ADAM33]], among others.<ref name=Hoffjan/> Many of these genes are related to the immune system or modulating inflammation. Even among this list of genes supported by highly replicated studies, results have not been consistent among all populations tested.<ref name=Hoffjan /> In 2006 over 100 [[gene]]s were associated with asthma in one [[genetic association]] study alone;<ref name=Hoffjan>{{cite journal | vauthors = Ober C, Hoffjan S | title = Asthma genetics 2006: the long and winding road to gene discovery | journal = Genes and Immunity | volume = 7 | issue = 2 | pages = 95–100 | date = March 2006 | pmid = 16395390 | doi = 10.1038/sj.gene.6364284 | s2cid = 1887559 | doi-access =  }}</ref> more continue to be found.<ref name="pmid20298365">{{cite journal | vauthors = Halapi E, Bjornsdottir US | title = Overview on the current status of asthma genetics | journal = The Clinical Respiratory Journal | volume = 3 | issue = 1 | pages = 2–7 | date = January 2009 | pmid = 20298365 | doi = 10.1111/j.1752-699X.2008.00119.x | s2cid = 36471997 | doi-access =  }}</ref>

Some genetic variants may only cause asthma when they are combined with specific environmental exposures.<ref name=Martinez2007/> An example is a specific [[single nucleotide polymorphism]] in the [[CD14]] region and exposure to [[endotoxin]] (a bacterial product). Endotoxin exposure can come from several environmental sources including tobacco smoke, dogs, and farms. Risk for asthma, then, is determined by both a person's genetics and the level of endotoxin exposure.<ref name=Martinez_CD14>{{cite journal | vauthors = Martinez FD | title = CD14, endotoxin, and asthma risk: actions and interactions | journal = Proceedings of the American Thoracic Society | volume = 4 | issue = 3 | pages = 221–5 | date = July 2007 | pmid = 17607003 | pmc = 2647622 | doi = 10.1513/pats.200702-035AW }}</ref>