<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>