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1、 TRISOMY21SYNDROMEDr XiaopingLuoProfessorandChairmanDepartmentofPediatricsTongjiHospitalofTongjiMedicalCollegeHuazhongUniversityofScienceandTechnologyWuhan China Downsyndrome asweknowittoday hasexistedsincethebeginningofhumankind Dept ofPediatrics TongjiHospital HUST Downsyndrome Firstdescribedinthe
2、medicalliteraturebyDr JohnLangdonDowninEnglandin1866In1956 scientistsdiscoveredthatthetypicalhumancellhas46chromosomesIn1958 LejeunediscoveredthatthecellsfromanindividualwithDShadanextrachromosome21In1959 9peoplewithDSwerefoundtohaveanextrachromosome21 1 Dept ofPediatrics TongjiHospital HUST Materna
3、lage 放射线Radiation Infection Chemicals Geneticfactors Mothercyesis Etiology TheincidenceofDS Maternalage Y Dept ofPediatrics TongjiHospital HUST MaternalAgeTheriskincreaseswiththematernalage Normal Thegenesofchromosome21 whatdoweknow Therearemorethan400genesonchromosome21 weusedtothinktherewerefewer
4、Ofthese 170codeforproteinsthatarealsoencodedbygenesinmiceandotheranimalsWhengenesareconservedacrossspecies itistypicallybecausetheyareimportant Chromosome21proteins ArepredictedtodirectlyandindirectlyaffectlearningandmemoryinDownsyndromebyPreventingestrogenfromenteringbraincells lowestrogeninbrainca
5、npromoteearlymenopauseandAlzheimerdisease ReducingsubstancesthatallowcellstocommunicatewithoneanotherReducingbraincellsurvivalintheadult Studyingchromosome21genesacrossspeciesallowsusto UnderstandtherolesofthesegenesinnormaldevelopmentandfunctionLearnhowtheproteinsencodedbythesegenesinteractwithothe
6、rproteinsinthebodyPredictwaysinwhichtheextrainformationencodedbythesegenescanbe turneddown or turnedoff bymedications genetherapy etc 2 TypesofDownSyndrome Trisomy21 92 95 MMoossaaiiccDDoowwnnSynnddrroommee 2 5 5 TranslocationTrisomy21 2 4 Trisomy21Foundin92 ofallDSindividualsCausedbynondisjuctionin
7、meiosis causingeggstohavetrisomy21Increasesinincidencewithmaternalage butalsofoundinyoungermothersChildrenbornimmediatelyafterDSchildrenhaveahigherchanceofalsohavingDS however forothersiblings theriskforhavingDSdoesnotincrease Nondisjunction MosaicDS2 4 oftheDSpopulationStartsoffwith23pairsofchromos
8、omesineachcellErroroccursinanearlycelldivisionDuringembryonicdevelopment arandomcellwillacquiretrisomy21 creating2individualcelllines normalandtrisomatic Theearlierthemutationoccurs themoreprofoundtheeffects MosaicDS TranslocationDS3 4 oftheDSpopulationARobertsoniantranslocationoccurswhenonechromoso
9、me21attachestoanotherchromosome formingasinglenew chromosomeTherecipientchromosomeisusuallychromosome14andthecombinationofthe2chromosomesiscalledafourteen twentyonetranslocationCanalsoswitchwith13 15 or22 3 TranslocationDSAbout ofTranslocationDSisinheritedTheparentisthencalledatranslocationcarrierPa
10、renthasonenormalcopyof21andonecopyof21attachedtoanotherchromosomeBothcopiesarethenpassedonWhenfertilizationoccurs embryocontainsbothcopiesof21fromthecarrierparent andthenormalonecopyor21fromthenormalparentEffectsaresimilartoTrisomy21DS TranslocationDS RobertsonianTranslocationsCanresultinDownsyndrom
11、e 4 MedicalComplications EpilepsyHypothyroidismCrossedeyesCataractsHearingimpairmentHeartdefectsChildhoodleukemiais20 morecommon HerniasSterilityinmalesFemalesarefertilebutcanpassonDSAcceleratedAgingwithhighchanceofAlzheimer sdisease 1968 1974 1983 8 1988 NewTestforDownSyndrome 1959 1966 1933 1990 S
12、creeningmilestones Trisomy21identifiedascauseofDownSyndrome Firstchromosomalanalysesfromamnioticfluid AssociationbetweenmaternalageandDownsyndrome Tripletestintroduced MaternalserummarkersforDownsyndrome Nuchaltranslucencyintroduced 1968 1974 1983 8 1988 1959 1966 1933 1990 1864 Langdon Downfirstdes
13、criptionoftheclinicalfeaturesof mongolism NoninvasiveprenatalscreeningforDSDecember1 2008 Sequenom Inc announcedresultsfromacollaborativestudywithTheChineseUniversityshowingthatitispreliminarilypossibletodiagnoseDownsyndromeonabloodsampletakenfromexpectantmothersduringthefirstandsecondtrimestersofpr
14、egnancy ThemethodusestechnologythatextractsfetalRNAfrommaternalblood Studyisbeinglaunchedtoevaluateupto10 000pregnanciesatincreasedriskforDS Noninvasivetest cont Atfirst womenwithpositivescreenswillssttiilllluunnddeerrggoochorionicvillisampling CVS oramniocentesistoconfirmresults butthehopeisthatthe
15、newtestwillultimatelyreplaceboth Thereissomeconcernthatthistestingwillbemarketed indemandbeforesufficientstudiesarecompletedtoproveaccuracy 5 Noninvasivetest cont ResearchersatStanfordhavepublishedpreliminaryresultsonamaternalblood basedDSscreenthatusesadifferenttechnologythanSequenomOthercompaniesa
16、realsoworkingonnoninvasivetests 1968 1974 1983 8 1988 AlternativeTherapiesforChildrenwithDownSyndrome1959 1966 1933 1990 Alternativetherapies history1960 s HenryTurkelclaimedthatamixtureof48ingredientscouldimprovetheintelligenceofchildrenwithDS whichheadministeredtohispatientsformorethan40years Nodouble blindstudywaseverperformed Noevidenceemergedthatthiswasbeneficial Alternativetherapieshistory cont 1980 s RuthHarrell andassociatesreportedthatsupplementaryvitaminsandmineralsandthyroidhormoneimp
