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RheumatologyMain111-120Q1A7-year-oldboyhasbeencomplainingoflefthippainforthepast8months.Overrecentweeks:hehasdevelopedalimp.Whenyouexaminehisgait,younotethathetakesshortstepswithhisleftleg.Onphysicalexamination,hislefthiphassignificantlylimitedrangeofmotion,andthereisatrophyoftheleftproximalthighmuscle.X-rayofthepatient'spelvisisshownbelow:Whichofthefollowingismostlikelyresponsibleforthispatient'scondition?A.SlippedepiphysisB.BoneinfectionC.OsteonecrosisD.MuscledystrophyE.SynovitisF.MalignancyA1Correctanswer:CX-rayofthispatient'spelvisshowsaflattenedandfragmentedleftfemora!head.Thealternatingregionsoflucencyanddensityreflectreplacementofnecroticbonebynewbone.Comparethecircledregionsbelow:Theseclinicalandradiographicfindingsarecharacteristicofidiopathicavascularnecrosisofthefemoralcapitalepiphysis,orLegg-Calve-Perthesdisease,Thisconditionmostcommonlyaffectsboysbetweenages4and10,withapeakincidencebetween5and7.Theclassicpresentationiship,groinorkneepainplusanantalgicgait.Ingeneral,thesepatientsaremanagedconservativelywithobservationandbracing,thoughsurgerymaybeindicatedincaseswherethefemora!headisnotwellcontainedwithintheacetabulum.(ChoiceA)Inslippedcapitalfemoralepiphysis(SCFE),themetaphysisandproximalfemursliprelativetotheepiphysisattheepiphysealplate.Thecapitalfemoralepiphysisremainsstructurallyintactwithintheacetabulum.Theclassicpresentationisanobeseadolescentmalewithcomplaintsofpain.(ChoiceB)Inpediatricpatients,themostcommonetiologyofosteomyelitisishematogenousseedingbyS.aureus.Theinfectiontendstoaffectthemetaphysis.withepiphysealsparing.Radiographicevidenceofosteomyelitisissubtleearlyinthecourseofthedisease.(ChoiceD)Duchennemusculardystrophy,themostcommonchildhoodmyopathy,causesproximalmuscleweaknessandcalfpseudohypertrophy.Thediseaseprogressestocompleteimmobilitybyearlyadolescence.Jointradiographsareusuallynormal.(ChoiceE)TransientsynovitisofthehipisacommoncauseoflimpInotherwisehealthychildren.Therearenoassociatedradiographicabnormalities.(ChoiceF)OsteosarcomaisaprimarybonecancerthatproducesafindingcalledCodman'striangleinthemetaphysesoflongbones.Ewingsarcomaisaprimarybonecancerthatcausessimilarradiographicfindings,butwhichtendtoaffectthediaphysesoflongbones.Educationalobjective:Unilateralsubacutehippaininamalechildcoupledwithaprogressiveantalgicgait,thighmuscleatrophy,decreasedhiprangeofmotion,andcollapseoftheipsilateralfemoralheadonplainpelvicx-raysarefindingssuggestiveofidiopathicavascularnecrosisofthefemoralcapitalepiphysis(Legg-Calve-Perthesdisease).Q2A16-year-oldboycomestotheofficeinDecemberduetorightkneeswellingthatbeganearlierthatdayfollowingsoccerpractice,althoughhedoesnotrecallanyspecificinjury.Thepatienthasmildassociatedpainandstiffness.Inaddition,overthelastseveralmonthshehasexperiencedfatiguewithoccasionalflu-likeillnessesandvariablejointpains.Thepatient'smedicalhistoryisunremarkable,andhetakesnomedications.HeisthecaptainofhishighschoolsoccerteamandspentthesummeratasoccercampinMaine.Thepatientissexuallyactivewithhisgirlfriendandusescondoms.Vitalsignsarenormal.Cardiopulmonaryexaminationisnormal.Thepatientisabletobearweightandhasagrosslynormalgait.Examinationoftherightkneeshowspalpablewarmthandamildeffusionbutnotenderness.Range-of-motlontestingshowsamilddecreaseinflexionintherightkneecomparedtotheleft.Otherjointsarenormal.Plainradiographsofthekneejointrevealnobonydeformity.Aspirationofthekneejointyieldsyellow-colored,translucentfluidwithaleukocytecountof20,000/m㎡(50%neutrophils)andnoorganismsonGramstain.Whichofthefollowingisthemostlikelycauseofthispatient'skneeswelling?A.Autoimmunesynovia!inflammationB.BorreliaburgdorferiinfectionC.DisseminatedgonococcalinfectionD.MeniscustearE.PriorChlamydiatrachomatisinfectionF.PriorstreptococcalthroatinfectionG.StaphylococcaljointinfectionA2Correctanswer:BThispatient'ssynovialfluidanalysisandhistoryofacutemonoarticulararthritisfollowingmonthsofmigratoryarthralgiasandatriptoiflameareconsistentwithLymearthritis,thehallmarkoflateLymedisease.LymediseaseiscausedbyBorreliaburgdorferi,aspirochetecarriedbythedeertick(Ixodesscapularis),andcausesdisseminatedinfectionbyhematogenousspreadandmigrationintovarioustissues.Earlysymptoms(eg,erythemamigrans,fever)canbeoverlookedormisdiagnosedifhistoryoftraveltoendemicareasisnotobtained.Untreatedearlylocalizeddiseasecanprogresstoaninflammatorymonoarticularorasymmetricoiigoarticuiararthritis,mostcommonlyinvolvingtheknee.Synovialfluidshowsaninflammatoryprofilewithanaverageleukocytecountof25,000/mm³;Gramstainandcultureareusuallynegative,althoughpolymerasechainreaction(doneforinvestigativepurposes)maydemonstrateBburgdorferiDNA.ThediagnosiscanbeconfirmedwithserumELISAandWesternblottesting.Oraldoxycyclineoramoxicillinisfirst-linetreatmentforLymearthritisIntheabsenceofconcurrentneurologicmanifestations.(ChoiceA)Autoimmunearthritis(eg,rheumatoidarthritis)typicallycausesachronic,symmetric,inflammatoryarthritisthatfavorsthesmalljoints.(ChoicesCandG)Staphylococcalanddisseminatedgonococcalinfectioncancauseanacuteinflammatorymonoarthritis