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  <xsd:element id="rare_OptionToPurchaseAdditionalCommonStockValuePerShare" name="OptionToPurchaseAdditionalCommonStockValuePerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="rare_OptionToPurchaseCommonStockValue" name="OptionToPurchaseCommonStockValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_OptionToSellCommonStockAggregateOfferingPrice" name="OptionToSellCommonStockAggregateOfferingPrice" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_OptionToSellCommonStockForCash" name="OptionToSellCommonStockForCash" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_OutstandingCashAndCashEquivalentsAcquired" name="OutstandingCashAndCashEquivalentsAcquired" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_PaymentForPurchaseOfCommonStock" name="PaymentForPurchaseOfCommonStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_PaymentFromSaleOfFutureRoyalties" name="PaymentFromSaleOfFutureRoyalties" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_PaymentsMadeUnderAgreement" name="PaymentsMadeUnderAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_PercentageOfGrossAccountsReceivableBalance" name="PercentageOfGrossAccountsReceivableBalance" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="rare_PercentageOfRightToReceiveRoyaltyPaymentsOnNetSales" name="PercentageOfRightToReceiveRoyaltyPaymentsOnNetSales" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_PremiumFromStockPurchaseAgreement" name="PremiumFromStockPurchaseAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ProceedsFromIssuanceOfCommonStockAtMarketOffering" name="ProceedsFromIssuanceOfCommonStockAtMarketOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ProceedsFromIssuanceOfCommonStockInConnectionWithLicenseAgreement" name="ProceedsFromIssuanceOfCommonStockInConnectionWithLicenseAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ProceedsFromRoyaltiesReceivedFinancingActivities" name="ProceedsFromRoyaltiesReceivedFinancingActivities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ProceedsFromSaleOfEquityInvestment" name="ProceedsFromSaleOfEquityInvestment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ProceedsFromSaleOfFutureRoyalties" name="ProceedsFromSaleOfFutureRoyalties" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ProfitLossSharingPercentageOnCommercializingProducts" name="ProfitLossSharingPercentageOnCommercializingProducts" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ProfitLossSharingPercentageOnNetSales" name="ProfitLossSharingPercentageOnNetSales" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_PurchasePriceOfSharesPurchasedOnExerciseOfCommonStockOption" name="PurchasePriceOfSharesPurchasedOnExerciseOfCommonStockOption" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_ReceivableRelatedToLicenseAgreementCurrent" name="ReceivableRelatedToLicenseAgreementCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_RegulatoryApprovalMilestones" name="RegulatoryApprovalMilestones" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_RegulatoryMilestonePayments" name="RegulatoryMilestonePayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_RelatedPartyPaymentOfContribution" name="RelatedPartyPaymentOfContribution" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_RelatedPartyTransactionContributionPeriod" name="RelatedPartyTransactionContributionPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_RemainingBusinessCombinationConsiderationTransferred1" name="RemainingBusinessCombinationConsiderationTransferred1" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_ResearchClinicalStudyAndManufacturingExpenses" name="ResearchClinicalStudyAndManufacturingExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_RevenueSharePercentageOnCommercializedProductsRangeMidToHigh" name="RevenueSharePercentageOnCommercializedProductsRangeMidToHigh" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_RoyaltiesTransactionCostsNet" name="RoyaltiesTransactionCostsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_RoyaltyAgreementTerminationDescription" name="RoyaltyAgreementTerminationDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_RoyaltyAgreementTerminationThresholdAmount" name="RoyaltyAgreementTerminationThresholdAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_RoyaltyPercentageOnNetSales" name="RoyaltyPercentageOnNetSales" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_SalesReserves" name="SalesReserves" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_SalesReservesAdjustments" name="SalesReservesAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_SalesReservesPayments" name="SalesReservesPayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_SalesReservesProvisions" name="SalesReservesProvisions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfVotingRightsOfAllClassesOfStock" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMinimumPercentageOfVotingRightsOfAllClassesOfStock" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantBeginningDate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantBeginningDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantEndingDate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesAvailableForGrantEndingDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_StockholdersEquityNoteNumberOfCommonSharesHeldAfterSplit" name="StockholdersEquityNoteNumberOfCommonSharesHeldAfterSplit" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_StockIssuedDuringPeriodSharesAtMarketOffering" name="StockIssuedDuringPeriodSharesAtMarketOffering" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_StockIssuedDuringPeriodSharesSecondaryIssues" name="StockIssuedDuringPeriodSharesSecondaryIssues" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_StockIssuedDuringPeriodValueAtMarketOffering" name="StockIssuedDuringPeriodValueAtMarketOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_StockIssuedDuringPeriodValueSecondaryIssues" name="StockIssuedDuringPeriodValueSecondaryIssues" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_StockPurchasedByUnderwritersPursuantToOptionGranted" name="StockPurchasedByUnderwritersPursuantToOptionGranted" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_TaxCreditCarryForwardExpirationYear" name="TaxCreditCarryForwardExpirationYear" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_TransactionPriceOfLicenseAgreement" name="TransactionPriceOfLicenseAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_TransferOfFairValueOnExerciseOfOptions" name="TransferOfFairValueOnExerciseOfOptions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_TransferOfFairValueOnExerciseOfOptionsCommonStock" name="TransferOfFairValueOnExerciseOfOptionsCommonStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="rare_UpforntCashPaymentPaid" name="UpforntCashPaymentPaid" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_UpfrontPayment" name="UpfrontPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_UpfrontPaymentForInProcessResearchAndDevelopmentExpense" name="UpfrontPaymentForInProcessResearchAndDevelopmentExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_UpfrontPaymentsOfCollaboration" name="UpfrontPaymentsOfCollaboration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="rare_CommitmentsAndContingenciesDisclosureLineItems" name="CommitmentsAndContingenciesDisclosureLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CostSharingPaymentsLineItems" name="CostSharingPaymentsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_IncomeTaxesDisclosureLineItems" name="IncomeTaxesDisclosureLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_LiabilityForSaleOfFutureRoyaltiesLineItems" name="LiabilityForSaleOfFutureRoyaltiesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OrganizationAndNatureOfBusinessLineItems" name="OrganizationAndNatureOfBusinessLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ScheduleOfFiniteAndIndefiniteLivedIntangibleAssetsLineItems" name="ScheduleOfFiniteAndIndefiniteLivedIntangibleAssetsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_StockholdersEquityLineItems" name="StockholdersEquityLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SummaryOfSignificantAccountingPoliciesLineItems" name="SummaryOfSignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_AbeonaMember" name="AbeonaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_AdditionalAtTheMarketSalesAgreementMember" name="AdditionalAtTheMarketSalesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ArcturusResearchCollaborationAndLicenseAgreementMember" name="ArcturusResearchCollaborationAndLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_BayerHealthCareLLCMember" name="BayerHealthCareLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_BaylorResearchInstituteLicenseAgreementMember" name="BaylorResearchInstituteLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CertificateOfDepositsAndTimeDepositsMember" name="CertificateOfDepositsAndTimeDepositsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CollaborationAgreementMember" name="CollaborationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CollaborationAndLicenseAgreementMember" name="CollaborationAndLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CollaborationAndLicenseMember" name="CollaborationAndLicenseMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CollaborationAndRoyaltyMember" name="CollaborationAndRoyaltyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CommercialAndDevelopmentActivityReimbursementsMember" name="CommercialAndDevelopmentActivityReimbursementsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CommonStockWarrantsExpiringOnTwoThousandTwentyMember" name="CommonStockWarrantsExpiringOnTwoThousandTwentyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CommonStockWarrantsExpiringOnTwoThousandTwentyOneMember" name="CommonStockWarrantsExpiringOnTwoThousandTwentyOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CommonStockWarrantsMember" name="CommonStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ComputerEquipmentAndSoftwareMember" name="ComputerEquipmentAndSoftwareMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ConvertiblePromissoryNoteMember" name="ConvertiblePromissoryNoteMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CrysvitaMember" name="CrysvitaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_DaiichiSankyoCoLtdMember" name="DaiichiSankyoCoLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_DebtSecuritiesInGovernmentSponsoredEntitiesMember" name="DebtSecuritiesInGovernmentSponsoredEntitiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_DevelopmentMilestoneMember" name="DevelopmentMilestoneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_DiaCartaLtdMember" name="DiaCartaLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_DimensionTherapeuticsIncMember" name="DimensionTherapeuticsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_DojolviMember" name="DojolviMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_EmploymentInducementPlanMember" name="EmploymentInducementPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_EuropeanUnionAndSwitzerlandAndTurkeyMember" name="EuropeanUnionAndSwitzerlandAndTurkeyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_FirstAnniversaryMember" name="FirstAnniversaryMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_GeneTxBiotherapeuticsLLCMember" name="GeneTxBiotherapeuticsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_GenetxMember" name="GenetxMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_GrantedMember" name="GrantedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_HeLAPCLPlatformMember" name="HeLAPCLPlatformMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_InvestmentInSolidCommonStockMember" name="InvestmentInSolidCommonStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_InvestmentsInArcturusAndSolidCommonStockMember" name="InvestmentsInArcturusAndSolidCommonStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_KyowaKirinCollaborationMember" name="KyowaKirinCollaborationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_LicenseAgreementMember" name="LicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_LicenseAndCollaborationAgreementMember" name="LicenseAndCollaborationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_LicenseAndTechnologyAccessAgreementMember" name="LicenseAndTechnologyAccessAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_LicensesAgreementMember" name="LicensesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_MahziTherapeuticsIncMember" name="MahziTherapeuticsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ManufacturingAndServicesMember" name="ManufacturingAndServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_MepseviiMember" name="MepseviiMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_MereoBioPharma3LimitedMember" name="MereoBioPharma3LimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_NonProfitFoundationMember" name="NonProfitFoundationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OmersMember" name="OmersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OpenMarketSaleMember" name="OpenMarketSaleMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OptionAndLicenseAgreementMember" name="OptionAndLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OptionsToPurchaseCommonStockRestrictedStockUnitsAndPerformanceStockUnitsMember" name="OptionsToPurchaseCommonStockRestrictedStockUnitsAndPerformanceStockUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OrphanDrugCreditsMember" name="OrphanDrugCreditsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OtherMember" name="OtherMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_PclAndHek293PlatformsMember" name="PclAndHek293PlatformsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_PerformanceStockOptionsMember" name="PerformanceStockOptionsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ProfitShareRevenueAndRoyaltiesMember" name="ProfitShareRevenueAndRoyaltiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ProgramAgreementAndUnitholderOptionAgreementMember" name="ProgramAgreementAndUnitholderOptionAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_RareDiseaseEducationAndAwarenessMember" name="RareDiseaseEducationAndAwarenessMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_RegeneronPharmaceuticalsIncMember" name="RegeneronPharmaceuticalsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_REGENXBIOIncorporatedMember" name="REGENXBIOIncorporatedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ResearchAndDevelopmentEquipmentMember" name="ResearchAndDevelopmentEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ResearchCollaborationAndLicenseAgreementCommercialMilestonesMember" name="ResearchCollaborationAndLicenseAgreementCommercialMilestonesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ResearchCollaborationAndLicenseAgreementDevelopmentMilestonesMember" name="ResearchCollaborationAndLicenseAgreementDevelopmentMilestonesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ResearchDevelopmentAndCommercializeAAVGeneTherapyProductsAgreementMember" name="ResearchDevelopmentAndCommercializeAAVGeneTherapyProductsAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_RightOfUseAssetsMember" name="RightOfUseAssetsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_RoyaltyPurchaseAgreementMember" name="RoyaltyPurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_RPIFinanceTrustMember" name="RPIFinanceTrustMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SaintLouisUniversityLicenseAgreementMember" name="SaintLouisUniversityLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SalesMilestoneMember" name="SalesMilestoneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SharesVestingMonthlyAfterFirstAnniversaryMember" name="SharesVestingMonthlyAfterFirstAnniversaryMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SolidAndArcturusMember" name="SolidAndArcturusMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SolidBiosciencesIncMember" name="SolidBiosciencesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_StockPurchaseAgreementMember" name="StockPurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SublicenseAgreementMember" name="SublicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SublicenseAgreementsMember" name="SublicenseAgreementsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_TimeDepositsMember" name="TimeDepositsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_TwoThousandElevenAndTwoThousandFourteenAndEmploymentInducementPlanMember" name="TwoThousandElevenAndTwoThousandFourteenAndEmploymentInducementPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_TwoThousandElevenEquityIncentivePlanMember" name="TwoThousandElevenEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_TwoThousandFourteenEmployeeStockPurchasePlanMember" name="TwoThousandFourteenEmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_TwoThousandFourteenIncentivePlanMember" name="TwoThousandFourteenIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_UnderwrittenPublicOfferingMember" name="UnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_UnitedStatesAndCanadaMember" name="UnitedStatesAndCanadaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_UniversityOfPennsylvaniaSchoolOfMedicineMember" name="UniversityOfPennsylvaniaSchoolOfMedicineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_USGovernmentTreasuryAndAgencySecuritiesMember" name="USGovernmentTreasuryAndAgencySecuritiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_AccrualsOfResearchAndDevelopmentCostsPolicyTextBlock" name="AccrualsOfResearchAndDevelopmentCostsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ConcentrationOfCreditRiskCreditLossesAndOtherRisksAndUncertaintiesPolicyTextBlock" name="ConcentrationOfCreditRiskCreditLossesAndOtherRisksAndUncertaintiesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_CommitmentsAndContingenciesDisclosureTable" name="CommitmentsAndContingenciesDisclosureTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_CostSharingPaymentsTable" name="CostSharingPaymentsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_IncomeTaxesDisclosureTable" name="IncomeTaxesDisclosureTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_LiabilitiesForSalesOfFutureRoyaltiesTable" name="LiabilitiesForSalesOfFutureRoyaltiesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_OrganizationAndNatureOfBusinessTable" name="OrganizationAndNatureOfBusinessTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_ScheduleOfFiniteAndIndefiniteLivedIntangibleAssetsTable" name="ScheduleOfFiniteAndIndefiniteLivedIntangibleAssetsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_StockholdersEquityTable" name="StockholdersEquityTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_SummaryOfSignificantAccountingPoliciesTable" name="SummaryOfSignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="rare_PropertyPlantAndEquipmentUsefulLivesTableTextBlock" name="PropertyPlantAndEquipmentUsefulLivesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfChangesInFairValueOfEquityInvestmentTableTextBlock" name="ScheduleOfChangesInFairValueOfEquityInvestmentTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfChangesInFairValueOfInvestmentInSecuritiesTableTextBlock" name="ScheduleOfChangesInFairValueOfInvestmentInSecuritiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfCollaborationAndRoyaltyRevenueTableTextBlock" name="ScheduleOfCollaborationAndRoyaltyRevenueTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfCostSharingPaymentsTableTextBlock" name="ScheduleOfCostSharingPaymentsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfSalesRelatedAccrualsAndAllowancesTableTextBlock" name="ScheduleOfSalesRelatedAccrualsAndAllowancesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfShareBasedPaymentAwardStockOptionsAndEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock" name="ScheduleOfShareBasedPaymentAwardStockOptionsAndEmployeeStockPurchasePlanValuationAssumptionsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_AvailableForSaleSecuritiesDebtSecuritiesPolicyTextBlock" name="AvailableForSaleSecuritiesDebtSecuritiesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_CollaborativeArrangementAndNoncollaborativeArrangementTransactionsDisclosureTextBlock" name="CollaborativeArrangementAndNoncollaborativeArrangementTransactionsDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_LiabilitiesForSalesOfFutureRoyaltiesTextBlock" name="LiabilitiesForSalesOfFutureRoyaltiesTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfActivityWithinLiabilityForSaleOfFutureRoyaltiesTableTextBlock" name="ScheduleOfActivityWithinLiabilityForSaleOfFutureRoyaltiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="rare_ScheduleOfIntangibleAssetsTableTextBlock" name="ScheduleOfIntangibleAssetsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
