MORPHOLOGYThe pathognomonic microscopic lesion of syphilis is a proliferative endarteritis with an accompanying inflammatory infiltrate rich in plasma cells. Endarteritishasacentralroleintissueinjuryatallsitesinvolvedbysyphilis,butitspathogenesisisnotunderstood;thereisnoevidencethatthespirochetescauseanydamagetohosttissuesdirectly.Instead,itisthoughtthatthehostimmuneresponseisresponsiblefortheendothelialcellactivationandproliferationthatisthehallmarkoftheendarteritis,whicheventuallyleadstoperivascularfibrosisandluminalnarrowing.
characteristiclesions.Thechancre ofprimarysyphilisistypically induratedandhasbeenreferredtoasahardchancre, to distinguishitfromthesoftchancreofchancroidcausedbyHaemophilus ducreyi (discussedlater).Theprimarychancreinmalesusuallyisontheglans,corona,orperianalregion.Infemales,multiplechancresmaybepresent,usuallyonthelabiaorvaginaaswellastheperianalregion.Thechancrebeginsasasmall,painless,firmpapule2to4weeksaftersexualexposure,whichgraduallyenlargestoproduceapainlessulcerwithwell-defined,induratedmarginsanda“clean,”moistbase(
Fig.18.20 ).Regionallymphnodesoftenareslightlyenlargedandfirm.Microscopicexaminationoftheulcerrevealsthetypicallymphocyticandplasmacyticinflammatoryinfiltrateandendarteritis.Spirochetesarereadilydemonstrableinhistologicsectionsofearlylesionswiththeuseofstandardsilverstains(e.g.,Warthin-Starrystains)orimmunohistochemicalstainsspecificforspirochetes.Withinapproximately2monthsofresolutionofthechancre,thelesionsofsecondarysyphilisappear.Themanifestationsofsecondarysyphilisarevariedbuttypicallyincludeacombinationofgeneralizedlymphnodeenlargementandavarietyofmucocutaneous lesions. Skinlesionsusuallyaresymmetricallydistributed;maybemaculopapular,scaly,orpustular;andcharacteristicallyinvolvethepalms of the hands and soles of the feet. Inmoistskinareas,suchastheanogenitalregion,innerthighs,andaxillae,broad-based,elevatedlesionstermedcondylomata lata mayappear(nottobeconfusedwithcondylomaacuminatacausedbyHPV)(Chapters18and23).Superficialmucosallesionsresemblingcondylomatalatacanoccuranywherebutareparticularlycommonintheoralcavityandpharynxandontheexternalgenitalia.Histologicexaminationofmucocutaneouslesionsduringthesecondaryphaseofthediseaserevealsthecharacteristicproliferativeendarteritisand,withspecialstainsorimmunohistochemistry,spirochetes,whichareoftenabundant.Lymphadenopathyismostcommonintheneckandinguinalareas.Histologicexaminationofenlargednodesdemonstrateshyperplasiaofgerminalcentersaccompaniedbyincreasednumbersofplasmacellsor,lesscommonly,granulomasorneutrophils.Lesscommonmanifestationsofsecondarysyphilisincludehepatitis,renaldisease,eyedisease(iritis),andgastrointestinalabnormalities.
Fig. 18.20 (A)Syphiliticchancreofthescrotum.Suchlesionstypicallyarepainlessdespitethepresenceofulceration,andtheyhealspontaneously.(B)Histologicfeaturesofthechancreincludeadiffuseplasmacellinfiltratebeneathsquamousepitheliumofskin.