General information of psoriasis in Western Medicine.docx

General information of psoriasis in Western Medicine.docx

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GeneralinformationofpsoriasisinWesternMedicine

GeneralinformationofpsoriasisinWesternMedicine

1.1Definitionofpsoriasis

Psoriasisisachronic,inflammatoryandsystemicdiseasethatmanifestsmostcommonlyaswell-circumscribed,erythematouspapulesandplaquesontheskinthatarecoveredwithsilveryscales.Usuallytheskinlesionsarepruriticandpainfulwithadherentthickscales,removalofthesescalesmayrevealpinpointbleeding.Thediseaseisachronicrecurringconditionthatvariesinseverityfromminorlocalisedpatchestocompletebodycoverage.Nailsandjointscanalsobeaffectedbypsoriasis

（1）.

1.2Pathologyandpathogenesisofpsoriasis

Theetiologyandpathogenesisofpsoriasishasnotbeencompletelydefinedbutitinvolvesimmunestimulationofepidermalkeratinocytes.Itinvolvesacompleximmunologicalandinflammatoryreaction

（1）.Thepathogenesisofpsoriasishasalargehereditarycomponent.Atleasteightchromosomallocihavebeenidentifiedforwhichstatisticallysignificantevidenceforlinkagetopsoriasishasbeenobserved（theselociareknownaspsoriasissusceptibility（PSORS）1to8）

（1）.Ofthesechromosomalloci,thehumanleukocyteantigen（HLA-Cw6allele/HLA-Cw0602–Cw0613）,alsoknownasPSORS1,isthekeysusceptibilitygeneforpsoriasis

（2）.Inadditiontogeneticfactors,environmentalfactorsincludinginfection,smoking,medications（e.g.betablockers,nonsteroidalanti-inflammatorydrugs（NSAIDs）,antimalarials,terbinafine,calciumchannelblockers,lipid-loweringdrugs,etc）,skininjury（Koebner’sphenomenon）andstressarethoughttoevokeaninflammatoryresponseandsubsequenthyperproliferationofkeratinocytes,resultinginpsoriasis（1,3）.

Thedevelopmentofpsoriasisisthoughttoinvolvesthefollowingprocess:

∙T-cellsactivateandmigrateintotheskinafterelementsoftheinnateimmunesystemareactivated（keratinocytesanddendriticcells）（3,4）;

∙FunctionalT-cellsincludingtype1helperTcells（Th1）andtype17helperTcells（Th17）growundertheinfluenceofcytokinessuchasinterleukin12（IL-12）andinterleukin23（IL-23）（3,4）;

∙Pro-inflammatorycytokinessuchastumournecrosisfactor-α（TNF-α）,IL-17andIL-22aresecretedbyTh1andTh17cellspromotingtheinflammatoryprocessinpsoriasis（3,4）;

∙Localskincellsincludingendothelialcells,fibroblasts,andkeratinocytesenhancethecutaneousimmuneresponsethroughexpressionofadhesionmoleculesandothermediators（3,4）.

Overall,psoriasisisanimmune-mediatedorgan-specific（skin,and/orjoint）inflammatorydiseaseinwhichintralesionalinflammationprimesbasalstemkeratinocytestohyperproliferateandperpetuatethediseaseprocess（3,4）.

1.3Epidemiologyofpsoriasis

1.3.1Prevalenceofpsoriasisinglobalgeneralpopulation

Althoughpsoriasisoccursworldwide,itsprevalencevariesconsiderably（5）.Itisreportedthattheaverageglobalprevalenceofpsoriasisisapproximately3%–4%.About15%-30%ofpsoriasissufferershavethesequelae‘psoriaticarthritis’,equatingtoapproximately0.5%–1%ofthetotalpopulation（6）.Table（chapter1-1）presentstheprevalencedatareportedinrecentsurveys.

Table（chapter1-1）Prevalenceofpsoriasisbycountry

Country

%withpsoriasis

Samplesize

China（7）

0.47

17,345

UK（8）

1.9

7,520,293

France（9）

5.2

6,887

Norway（10）

8.5

18,747

USA（11）

2.2

27,220

USA（12）

3.15

2,984

USA（Caucasianpopulation）（13）

2.5

21,921

USA（Africanpopulation）（13）

1.3

2,443

Australia（Victoria）（14）

6.6

1,457

1.3.2Factorsimpactingontheprevalenceofpsoriasis

Thereportedprevalencesurveysdifferinmanyregards,namelygeographicaloriginofthestudy,definitionofprevalenceontimepoint,period,andlifetimeofpsoriasis,samplingmethods,andwhetheritisself-reportedordiagnosisconfirmedbyphysician.Mostofthesestudiesarebasedonself-reporteddiagnosis,whichmayleavemildcasesofpsoriasis,e.g.naildisease,undiagnosed.Moreover,theelusiveaetiologyofskindiseasesandthelackofpreciseclassificationcriteriaforpsoriaticarthritismayalsoleadtomisdiagnosis（6）.

Geographicandethnicfactorsalsocontributetodifferencesinpsoriasisprevalence.Forinstance,theprevalenceincoolerregionsishigherthanthatofotherregions（15）.Inaddition,lowerprevalenceisobservedamongAfricanAmericans（1.3%）,comparedwiththeCaucasianAmericanpopulation（2.5%）（13）.

Multi-factorialcomponentssuchasphysicalenvironment,geneticfactors,gender,ageandbehaviouralpatternsplayaroleintheprogressionofpsoriasis（15）.

Ithasbeensuggestedthattheonsetofpsoriasisoccursatayoungerageinfemalepatientscomparedwithmales,whichresultsinahigherprevalenceinyoungfemalepatients（16）.Furthermore,themeanageofonsetforthefirstpresentationofpsoriasisisbetween15–20years,withasecondpeakoftenoccurringbetween55–60years,andthenasignificantdeclineaftertheageof70years,irrespectiveofgender（16）.

1.3.3Riskfactorsofpsoriasis

Theriskfactorsofpsoriasisarenotwelldefined.However,obesityisbelievedtobeassociatedwithpsoriasisaspatientshaveahigherbodymassindexcomparedwiththenon-psoriaticpopulation（17）.Smokingislikelytoplayaroleintheonsetofpsoriasis（18）andalcoholmayinfluencetheprogressionofthedisease（19）.Stressisanimportanttriggerfactorandmayinfluencethedevelopmentofthecondition（20）.Furthermore,somemedicationsmaybeassociatedwiththeonsetorexacerbationofpsoriasis,includingantimalarialmedications,NSAIDs,β-blockers,lithiumsaltsandwithdrawalfromsteroids（21）.Bacterialinfectionsmayalsotriggerorexacerbatepsoriasis（21）.Conversely,theconsumptionoffruitandvegetables,carrots,tomatoesandβ-carotenecandecreasetheriskofpsoriasis（22）.

1.3.4Impactofpsoriasis

1.3.4.1Qualityoflife

Psoriasisitselfisnotalife-threatingconditionhowever,ithasasignificantimpactonthesufferers’qualityoflife.Thepsychologicalcomorbiditiesofpsoriasiscansignificantlyimpairapatients’qualityoflife（23-25）.Onestudycomparedqualityoflifeinpeoplewithpsoriasiswithpeoplewhohaveotherdiseases,andfoundthatthequalityoflifeofpatientswithpsoriasiswasmoreseverethanthatofpatientswithdiabetes,coronaryheartdiseaseandcancer（26）.Besidesthepatient'sappearance,theamountoftimerequiredtotreatextensiveskinorscalplesionsandtomaintainclothingandbeddingadverselyaffectsqualityoflifeaswell.Inaddition,arthriticpsoriasiscanalsoresultinincreasinganddebilitatingjointpainandstiffnessandimpairedmovement（27）.

1.3.4.2Economicburden

Generally,thecostofdiseaseconsistsofdirectcostsincludingdiagnosticprocedures,therapiesandhospitaladmissionsandindirectcostsincludingworkabsenteeism,earlyretirement,andunemployment.Thecostofpsoriasisisconsiderablebecauseofitslong-termduration.StudiesinGermanysuggestedthattheaverageannualcostsofmildpsoriasisvulgarisperpatientrangedfrom500€to2,000€andforseverediseasefrom4,000€to10,000€（28,29）.Theindirectcostwasestimatedtobeabout1,600€perpersonperannum（29）.AsurveyinvestigatingpatientswithpsoriasisintheUnitedKingdomindicatedthatanaveragepsoriasispatientwasabsentfromworkfor26daysayear.InAmerica,psoriasiscostsUS$11.3billioninhealthcareannually（whencalculatedat2%prevalence）andthelossinproductivityfrompsoriasisisaroundUS$16.5billionperyear（30）.

1.4Diagnosisofpsoriasis

1.4.1Typesofpsoriasis

Psoriasisisclassifiedintosevencategories:

1.Plaquepsoriasis（psoriasisvulgaris）

Plaquepsoriasisisthemostcommontypeofpsoriasis,observedinapproximately80%to90%ofpatients

（1）.Plaquepsoriasisappearsassharplymarginated,erythematouspatchesorplaqueswithacharacteristicsilvery-whitemicaceousscale（31）.Theplaquesareroundorovalinshapeandaretypicallylocatedonthescalp,trunk,buttocksandlimbs,especiallyonextensorsurfacessuchastheelbowsandknees

（1）.

2.Guttatepsoriasis

Typicalmanifestationisdew-drop-like,1to15mm,salmon-pinkpapules,usuallywithafinescale.Itisfoundprimarilyonthetrunkandtheproximalextremities.AhistoryofupperrespiratoryinfectionwithgroupAbeta-hemolyticstreptococcioftenprecedesguttatepsoriasis.Thediseaseismostcommonduringchildhoodoradolescenceandcantransitionintopsoriasisvulgaris（1,3）.

3.Inversepsoriasis

Inversepsoriasiscommonlyappearsintheinframammaryandabdominalfolds,groin,axillae,andgenitalia.Thelesionsappearaserythematousplaqueswithsmallscales（1,3）.

4.Naildisease

Thecharacteristicsofnailpsoriasisincludepitting,onycholysis,subungualhyperkeratosis,andtheoil-dropsign（atranslucentdiscolourationinthenailbedthatresemblesadropofoilbeneaththenailplate）.Nailpsoriasisusuallyaffectsnailsonthehandsmoreoftenthanthefeet.Itisseenin90%ofpatientswithpsoriaticarthritis

（1）.

5.Psoriaticarthritis

Psoriaticarthritisisaninflammatoryseronegativespondyloarthropathyassociatedwithpsoriasis.Thecharacteristicsofpsoriaticarthritisarestiffness,pain,swelling,andtendernessofthejointsandsurroundingligamentsandtendons（dactylitisandenthesitis）.Theseverityofthearthritisusuallydoesnotcorrelatewiththeskindisease.Naildamageisverycommoninpsoriaticarthritis.Theradiographicfeaturesofpsoriaticarthritismainlyinvolvejointerosion,jointspacenarrowing,andbonyproliferation（32）.

6.Pustularpsoriasis

Pustularpsoriasisconsistsofgeneralisedandlocalisedtypes.Generalisedpustularpsoriasisshowswidespread