USMLE题库Dermatology1-10

Dermatology题库Q1A56-year-oldmaleisbroughttotheemergencydepartmentwithnew-onsettonic-clonicseizures.Hispastmedicalhistoryisinsignificant.MRIofthebrainrevealsaround1.6cmmassintherighttemporallobe.Afterinitialevaluation,astereotacticbiopsyofthemassisobtained.ThebiopsyresultsshowaneoplastictissuecontainingamutationinthegenethatencodesBRAF,aproteinkinase.Thepointmutationresultsinasubstitutionofglutamicacidforvalineatposition600oftheprotein.Whichofthefollowingisthemostlikelydiagnosis?A.GlioblastomaB.MelanomaC.ProstatecancerD.RenalcellcarcinomaE.SmallcelllungcancerA1Correctanswer:BThemainenvironmentalriskfactorforcutaneousmelanomaisincreasedexposuretoultravioletradiation.Exposuretobothsolarandtanning-bedultravioletsourcesincreasestheriskofdevelopingcutaneousmelanoma,asultravioletradiationcancausemalignanttransformationofmelanocytes.Thisriskisalsoincreasedbymutationsinspecificgeneticfactors,mostcommonlytumorsuppressorgenesandvariousoncogenes.BRAFisaproteinkinaseinvolvedinactivatingthesignalingpathwaysofmelanocyteproliferation,andtheBRAFmutationV600E(valinereplacedbyglutamate)isseenin40-60%ofpatientswithmelanoma.TheBRAFmutationleadstogreatlyincreasedactivationofthesignalingpathwaysformelanocytegrowth,survival,andmetastasis.RecentstudieshaveshownthatVemurafenib(apotentinhibitorofmutatedBRAF)hadsignificantanti-tumoreffectswithimprovedsurvivalandlong-termoutcomesinstage3and4,V600Epositivemelanomapatients.Thispatient'spresenceofBRAFmutationinthetissuemostlikelyindicatesadiagnosisofmetastaticmelanoma.(ChoiceA)Glioblastomahasbeenassociatedwithoverexpressionofgrowthfactors(suchasPDGF,EGFR,sIGF,andTGF),buthasnotbeenassociatedwiththeBRAFmutation.(ChoiceC)ThepresenceofBRCA1andBRCA2increasestheriskofprostatecancer,butBRAFhasnotbeenassociatedwithanincreasedrisk.(ChoicesDandE)Renalcellcarcinomaandsmallcelllungcancerappeartobemultifactorialinorigin,involvingmanydifferentgenesandenvironmentalfactors.However,BRAFhasnotbeenassociatedwitheithermalignancy.Q2A64-year-oldmanpresentstothephysician'sofficewithsevereleft-sidedchestpainthatstartedfourdaysago.Hedescribesthepainasconstantandburning.Yesterdayhealsonotedonsetofarash.Physicalexaminationrevealsavesicularrashlocatedin5thleftintercostalspace.Whichofthefollowingpathologicfindingswouldyouexpectmostintheaffectedarea?A.AcantholysisandintercellularIgGdepositsB.MicroabscessesatthetipsofdermalpapillaeC.Multinucleatedinclusion-bearinggiantcellsD.KoilocytosisofthesuperficialepidermallayersE.Eosinophiliccytoplasmicinclusions(molluscumbodies)Correctanswer:CVaricella-zostervirus(VZV)isanenvelopeddouble-strandedDNAvirus.InfectionwithVZVproducestwotypesofclinicalmanifestations.Thefirstcontactwiththisvirusviarespiratoryrouteresultsinvaricella(chickenpox).Itisgenerallyabenigndiseaseofchildhood,butmayalsoaffectnon-immuneadults.Afterresolutionofsymptoms,VZVtravelsviasensoryfiberstothedorsalrootgangliaofthespinalcordwhereitremainsdormantforyears.Weakeningofcellularimmunityleadstoreactivationofthevirusthatmanifestsasherpeszoster(shingles).Clinicallyherpeszostermanifestswithaburningsensationand/orpainunilaterallyinadermatomaldistribution.In2-3daysanerythematousmaculopapularrashdevelopsintheaffecteddermatome.Thepapulestransformintothevesiclesthatlatercoalesce.Ruptureofthevesiclesproducesulcersthatcrustinafewweeks.Thepatientiscontagiousuntilthelesionsaredry.Lightmicroscopyofasamplefromavesiclebaserevealsintranuclearinclusionsinkeratinocytesandmultinucleatedgiantcells(positiveTzancksmear).Skinbiopsywouldshowacantholysis(lossofintercellularconnections)ofkeratinocytesandintraepidermalvesicles.Dermalinflammatoryinfiltrationandleukocytoclasticvasculitismaybepresent.(ChoiceA)Acantholysisformingsuprabasalblistersisthetypicalmicroscopicappearanceofpemphigusvulgaris(PV).ImmunofluorescencerevealsdepositionofIgG-containingdepositsinareticularpatternaroundkeratinocytes.TheimmunetargetinPVisthedesmosomeproteindesmoglein3.(ChoiceB)Dermatitisherpetiformispresentswithpruriticgroupedvesiclesontheextensorsurfaces.Lightmicroscopyrevealsaccumulationsofneutrophilsonthetipsofdermalpapillae(microabscesses).(ChoiceD)HPVinfectionoftheskinpresentswithwarts(verrucavulgaris)orsquamouscellcarcinomaofthepenisorvulvadependingontheHPVtype.Lightmicroscopyrevealscytoplasmicvacuolesinkeratinocytes(koilocytosis)andhyperplasiaoftheepidermis.(ChoiceE)Infectionbymolluscumcontagiosum,apoxvirus,causeseosinophiliccytoplasmicinclusions(molluscumbodies)ininfectedcellsanddome-shapedumbilicatedpapulesonexam.A2Q3A64-year-oldCaucasianmalepresentstoyourofficewithbullouslesionsonhislowerabdomenandgroin.Skinbiopsysuggestsbullouspemphigoidinthispatient.Thepatient'sserumismostlikelytocontainantibodiesagainstwhichofthefollowing?A.KeratinB.DesmosomeC.Collagen,typeIVD.FibronectinE.GapjunctionF.HemidesmosomeA3Correctanswer:FPrimarilyadiseaseoftheelderly,bullouspemphigoidisanautoimmuneconditioncharacterizedbyantibodiesthatattackhemidesmosomesalongthebasementmembraneofthedermal-epidermaljunction.Theactivityoftheseautoantibodiesresultsincomplementfixation,andthere