<Patient xmlns="http://hl7.org/fhir">
    <id value="aaaaaaaa" />
    <extension url="http://example.org/extensions/patient-age">
        <valueAge>
            <value value="30" />
            <unit value="years" />
            <system value="http://unitsofmeasure.org" />
            <code value="a" />
        </valueAge>
    </extension>
    <identifier>
        <system value="http://example.com/patient" />
        <value value="aaaaaaaa" />
    </identifier>
    <name>
        <given value="aaaaaaaa" />
    </name>
    <gender value="male" />
</Patient>