希氏内科学 哮喘

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1、Goldman:CecilMedicine,23rded.Copyright©2007Saunders,AnImprintofElsevierChapter87–ASTHMAJeffreyM.DrezenDefinitionAsthmaisaclinicalsyndromeofunknownetiologycharacterizedbythreedistinctcomponents:(1)recurrentepisodesofairwayobstructionthatresolvespontaneouslyorasares

2、ultoftreatment;(2)exaggeratedbronchoconstrictorresponsetostimulithathavelittleornoeffectinnonasthmaticsubjects,aphenomenonknownasairwayhyperresponsiveness;and(3)inflammationoftheairwaysasdefinedbyavarietyofcriteria.Althoughairwayobstructionislargelyreversible,itis

3、currentlythoughtthatchangesintheasthmaticairwaymaybeirreversibleinsomesettings.EpidemiologyAsthmaisanextremelycommondisorderaffectingboysmorecommonlythangirlsand,afterpuberty,womenslightlymorecommonlythanmen;approximately7%oftheadultpopulationoftheUnitedStateshass

4、ignsandsymptomsconsistentwithadiagnosisofasthma.Althoughmostcasesbeginbeforetheageof25years,asthmamaydevelopatanytimethroughoutlife.Theworldwideprevalenceofasthmahasincreasedmorethan45%sincethelate1970s.Thegreatestincreasesinasthmaprevalencehaveoccurredincountries

5、thathaverecentlyadoptedan“industrialized”lifestyle.Althoughavarietyoftheorieshavebeenproposed,thereasonsfortheoverallincreaseinprevalenceofasthmaarenotknown.Asthmaisamongthemostcommonreasonstoseekmedicaltreatment.IntheUnitedStates,itisresponsibleforabout15milliona

6、nnualoutpatientvisitstophysiciansandfornearly2millionannualinpatienthospitaldaysoftreatment.Theyearlydirectandindirectcostsofasthmacarearemorethan$8billion;morethan80%ofthesecostsareattributabletodirectexpendituresonmedicalcareencountersorasthmamedications.Pathobi

7、ologyGeneticsIntwinstudies,asthmahasabout60%heritability,indicatingthatbothgeneticandenvironmentalfactorsareimportantinitsetiology.Despitethisevidenceforasubstantialgeneticcontributiontothebiologyofasthmaandidentificationofanumberofcandidategenes,nodiscoveredgenet

8、icvarianthasenhancedriskfortheasthmaphenotypeacrossallpopulations.Thesedatasuggestthatmultiplegeneticvariantsaccountfortheheritabilityofasthmainagivenin