USMLE题库Dermatology11-23

Dermatology题库Q11A31-year-oldwomancomestothephysicianwithavelvetyskinrashinheraxilla,asshownintheimagebelow.Whichofthefollowingisthemostlikelycauseofthispatient'scondition?A.CalcitoninhypersecretionB.InsulinresistanceC.SerotoninhypersecretionD.TestosteroneunresponsivenessE.VitaminDresistanceA11Correctanswer:CThisimageshowsthetypicalpresentationofacanthosisnigricans(AN),whichoccursmostcommonlyinflexuralareas.Themostcommonlocationsaretheaxillae,posteriorneck,andgroin,butitmayappearonotherareasofthebodysuchasthepalms,soles,andoralmucosa&vermilionborder.Onphysicalexamination,theselesionsappearashyperkeratotic,hyperpigmentedplaqueswithaclassicuvelvetyutexture.Skintags(acrochordons)arepedunculatedoutgrowthsofnormalskinthatarecommonlypresentonregionsaffectedbyacanthosisnigricans.ANisassociatedwithanumberofdiseases.Dependingontheunderlyingcondition,itisdividedintobenignandmalignantforms.1.BenignANiscommonlyassociatedwithinsulinresistance.Increasedlevelsofinsulinandinsulin-likegrowthfactorsstimulateepidermalanddermalproliferation.2.MalignantANisassociatedwithunderlyingneoplasms,especiallyofthegastrointestinalandgenitourinarytracts.Thesuddenappearanceofsuchskinchangesinmiddle-agedorelderlypatientsissuggestiveofunderlyingmalignancy.GastricadenocarcinomaisthemostcommoncauseofmalignantAN.(ChoicesAandE)Hypersecretionofcalcitonin(asinmedullarythyroidcancer)andvitaminDresistancearenotassociatedwithAN.(ChoiceC)Hypersecretionofserotonincanoccurwithcarcinoidtumors,includingthegastrointestinalvariety.However,excessserotoninitselfdoesnotcauseAN.(ChoiceD)Testosteroneunresponsiveness(androgeninsensitivitysyndrome,testicularfeminizationsyndrome)developsduetoadefectintestosteronereceptorsinperipheraltissues.Suchpatientsarephenotypicfemaleswhopresentwithprimaryamenorrhea.Theuterusisabsentandthevaginaendsasablindpouch,butbreastdevelopmentisnormalduetotheproductionofestrogenbyaromatase.Q12A31-year-oldCaucasianfemalepresentstoyourofficeforroutinecheck-up.YounoticeseveralsubcutaneousbumpsthatseemtobeattachedtoAchillestendons.Herfatherdiedfromaheartattackat35yearsoldandhermothersuffersfromrheumatoidarthritis.Herauntwasdiagnosedwithcoloncancerwhile55yearsold.Whichofthefollowingisthebestinitialtestinthispatient?A.BloodcholesterolB.FastingbloodglucoseC.RheumatoidfactorD.AntinuclearantibodiesE.FecaloccultbloodtestA12Correctanswer:ATypicallyassociatedwithhyperlipidemiaorlymphoproliferativemalignancies,xanthomasareyellownodulescomposedoflipid-ladenhistiocytesinthedermis.Clinically,xanthomascanbedividedintofivecategories:eruptivexanthomas(yellowpapulesthatabruptlyappearwhenplasmatriglyceridesandlipidsincrease);tuberousandtendinousxanthomas(thelatterareoftenpresentonAchillestendonsandtheextensortendonsofthefingers);planexanthomas(linearlesionsinskinfoldsthatarestronglyassociatedwithprimarybiliarycirrhosis);andxanthelasma(softeyelidorperiorbitalplaqueswithnoassociatedlipidabnormalitiesin50%ofaffectedindividuals).Histologically,xanthomasarecomposedofbenignmacrophagespackedwithfinelyvacuolated,ufoamyHcytoplasm.Thiscytoplasmcontainshighlevelsofcholesterol,phospholipids,andtriglycerides.Thelipid-ladenmacrophagesarefrequentlyalsoenclosedbyinflammatorycellsandfibroticstroma.Withxanthelasmas,thesmallaggregatesofdermalfoamcellsarepresentwithoutanysurroundinginflammationorfibrosis.(ChoiceB)Fastingbloodglucosewouldbeappropriatetoevaluateinpatientssuspectedofhavingdiabetesmellitusorotherglucosemetabolicabnormalities.(ChoiceC)Rheumatoidfactorwouldbeappropriatetoevaluateinpatientssuspectedofhavingrheumatoidarthritis.(ChoiceD)Antinuclearantibodieswouldbeappropriatetoevaluateinpatientssuspectedofhavingautoimmunediseasessuchassystemiclupuserythematosus.(ChoiceE)Fecaloccultbloodtestwouldbeappropriatetoevaluateinpatientssuspectedofhavingbleedingofthegastrointestinaltract.Q13A23-year-oldmalewhojuststartedtreatmentforstreptococcaltonsillitispresentstotheERwithapruriticskinrash.Theskinlesionsobservedonphysicalexaminationareshownontheslidebelow.Biopsyofthelesionsismostlikelytoshow:A.AcanthosisB.EpidermalspongiosisC.AcantholysisD.DyskeratosisE.DermaledemaA13Correctanswer:EUrticaria,or”hives，isacommon,transientdermatologicdisorderthatarisessecondarytotheantigen-induceddegranulationoffocalmastcellsthroughIgEantibodysensitization.Alternatively,anIgE-independenturticariacanalsodevelopafterexposuretosubstancesthatdirectlystimulatemastcelldegranulation(eg,opiates,antibiotics,andradiographiccontrastmedia).Bothdegranulationpathwayscausemicrovasculaturehyperpermeabilityandtheformationofwhealsthattypicallysurfaceandresolvewithinhours,withsomeepisodespersistingfordaystomonths.Thelesionsmaycoalesceintolargerlesionsthatassumeannular,linear,oraeriformshapes.Histologically,urticariapresentswithsubtlefeatures.Amild,superficialinfiltratecomposedofmononuclearcellsandoccasionaleosinophilsisobservedimmediatelyarounddermalvenules.Superficially,thecollagenbundlesarepartedbydermaledemaandthelymphaticchannelsaredilatedwithexcesstransudate.Epidermalchangesarenotidentified.(ChoiceA)Acanthosisdes