curl -X GET "https://api.omophub.com/v1/concepts/320128/relationships" \
  -H "Authorization: Bearer YOUR_API_KEY"

{
  "success": true,
  "data": {
    "concept_id": 320128,
    "concept_name": "Essential hypertension",
    "relationships": [
      {
        "relationship_id": "Is a",
        "target_concept_id": 316866,
        "target_concept_name": "Hypertensive disorder",
        "target_concept_code": "38341003",
        "target_vocabulary_id": "SNOMED",
        "target_domain_id": "Condition",
        "relationship_direction": "outbound",
        "valid_start_date": "1970-01-01",
        "valid_end_date": "2099-12-31"
      },
      {
        "relationship_id": "Subsumes",
        "target_concept_id": 4124681,
        "target_concept_name": "Accelerated hypertension",
        "target_concept_code": "48146000",
        "target_vocabulary_id": "SNOMED",
        "target_domain_id": "Condition",
        "relationship_direction": "inbound",
        "valid_start_date": "1970-01-01",
        "valid_end_date": "2099-12-31"
      },
      {
        "relationship_id": "Maps to",
        "target_concept_id": 435216,
        "target_concept_name": "Essential hypertension",
        "target_concept_code": "I10",
        "target_vocabulary_id": "ICD10CM",
        "target_domain_id": "Condition",
        "relationship_direction": "outbound",
        "valid_start_date": "1970-01-01",
        "valid_end_date": "2099-12-31"
      },
      {
        "relationship_id": "Has finding site",
        "target_concept_id": 4103720,
        "target_concept_name": "Cardiovascular system",
        "target_concept_code": "113257007",
        "target_vocabulary_id": "SNOMED",
        "target_domain_id": "Spec Anatomic Site",
        "relationship_direction": "outbound",
        "valid_start_date": "1970-01-01",
        "valid_end_date": "2099-12-31"
      }
    ],
    "relationship_summary": {
      "total_relationships": 4,
      "relationship_types": ["Is a", "Subsumes", "Maps to", "Has finding site"],
      "target_vocabularies": ["SNOMED", "ICD10CM"],
      "target_domains": ["Condition", "Spec Anatomic Site"]
    }
  },
  "meta": {
    "request_id": "req_relationships_123",
    "timestamp": "2024-12-22T10:00:00Z",
    "vocab_release": "2025.2"
  }
}