{
  "resourceType": "StructureDefinition",
  "id": "MyPatientProfile",
  "url": "http://example.org/fhir/StructureDefinition/MyPatientProfile",
  "name": "MyPatientProfile",
  "status": "draft",
  "description": "A custom Patient profile that makes birthDate required and adds a blood group extension.",
  "fhirVersion": "4.0.1",
  "kind": "resource",
  "abstract": false,
  "type": "Patient",
  "baseDefinition": "http://hl7.org/fhir/StructureDefinition/Patient",
  "derivation": "constraint",
  "differential": {
    "element": [
      {
        "id": "Patient.birthDate",
        "path": "Patient.birthDate",
        "min": 1
      },
      {
        "id": "Patient.extension:blood-group",
        "path": "Patient.extension",
        "sliceName": "blood-group",
        "min": 0,
        "max": "1",
        "type": [
          {
            "code": "Extension",
            "profile": [
              "http://example.org/fhir/StructureDefinition/blood-group"
            ]
          }
        ]
      }
    ]
  }
}