description: Extension to capture the age at onset of a condition. This backports the onsetAge functionality from FHIR R5 to R4.
package_name: de.medizininformatikinitiative.kerndatensatz.seltene
derivation: constraint
name: OnsetAge
type: Extension
elements:
  extension: {index: 0}
  url:
    pattern: {type: Uri, value: 'https://www.medizininformatik-initiative.de/fhir/ext/modul-seltene/StructureDefinition/mii-ext-seltene-onset-age'}
    index: 1
  value:
    short: Alter bei Erkrankungsbeginn
    mustSupport: true
    choices: [valueAge]
    index: 3
  valueAge: {type: Age, short: Alter bei Erkrankungsbeginn, mustSupport: true, choiceOf: value, index: 4}
  value[x]:
    elements:
      value: {short: Numerischer Alterswert, index: 5}
      unit: {short: Alterseinheit, index: 6}
      system:
        pattern: {type: Uri, value: 'http://unitsofmeasure.org'}
        index: 7
      code:
        short: UCUM-Code für Alterseinheit
        binding: {strength: required, valueSet: 'http://hl7.org/fhir/ValueSet/age-units'}
        index: 8
    required: [value, unit, system, code]
package_version: 2026.0.0-ballot
extensions: {}
class: extension
kind: complex-type
url: https://www.medizininformatik-initiative.de/fhir/ext/modul-seltene/StructureDefinition/mii-ext-seltene-onset-age
base: http://hl7.org/fhir/StructureDefinition/Extension
version: 2026.0.0-ballot