diff --git a/src/dcd_mapping/mavedb_data.py b/src/dcd_mapping/mavedb_data.py
index 1dad2b2..ed0606b 100644
--- a/src/dcd_mapping/mavedb_data.py
+++ b/src/dcd_mapping/mavedb_data.py
@@ -27,6 +27,7 @@
     MAVEDB_BASE_URL,
     authentication_header,
     http_download,
+    is_missing_value,
 )
 from dcd_mapping.schemas import (
     ScoreRow,
@@ -246,13 +247,13 @@ def _load_scoreset_records(
     with path.open() as csvfile:
         reader = csv.DictReader(csvfile)
         for row in reader:
-            if row["score"] == "NA":
+            if is_missing_value(row["score"]):
                 row["score"] = None
             else:
                 row["score"] = row["score"]
-            if row["hgvs_nt"] != "NA":
+            if not is_missing_value(row["hgvs_nt"]):
                 prefix = row["hgvs_nt"].split(":")[0] if ":" in row["hgvs_nt"] else None
-            elif row["hgvs_pro"] != "NA":
+            elif not is_missing_value(row["hgvs_pro"]):
                 prefix = (
                     row["hgvs_pro"].split(":")[0] if ":" in row["hgvs_pro"] else None
                 )
diff --git a/src/dcd_mapping/resource_utils.py b/src/dcd_mapping/resource_utils.py
index ef29402..b72cc56 100644
--- a/src/dcd_mapping/resource_utils.py
+++ b/src/dcd_mapping/resource_utils.py
@@ -10,6 +10,25 @@
 
 _logger = logging.getLogger(__name__)
 
+# Common representations of missing/null data in CSV files
+MISSING_VALUE_REPRESENTATIONS = frozenset(
+    {
+        "NA",
+        "N/A",
+        "na",
+        "n/a",
+        "NaN",
+        "nan",
+        "null",
+        "NULL",
+        "None",
+        "none",
+        "",
+        "-",
+        ".",
+    }
+)
+
 MAVEDB_API_KEY = os.environ.get("MAVEDB_API_KEY")
 MAVEDB_BASE_URL = os.environ.get("MAVEDB_BASE_URL")
 ENSEMBL_API_URL = os.environ.get("ENSEMBL_API_URL", "https://rest.ensembl.org")  # TODO
@@ -24,6 +43,22 @@
     LOCAL_STORE_PATH.mkdir(exist_ok=True, parents=True)
 
 
+def is_missing_value(value: str | None) -> bool:
+    """Check if a value represents missing/null data.
+
+    This function recognizes multiple common representations of missing data
+    that may appear in CSV files from external sources, making the codebase
+    more resilient to upstream changes in NA representation.
+
+    :param value: The value to check
+    :return: True if the value represents missing data, False otherwise
+    """
+    if value is None:
+        return True
+    # Strip whitespace and check against known missing value representations
+    return value.strip() in MISSING_VALUE_REPRESENTATIONS
+
+
 def authentication_header() -> dict | None:
     """Fetch with api key envvar, if available."""
     return {"X-API-key": MAVEDB_API_KEY} if MAVEDB_API_KEY is not None else None
diff --git a/src/dcd_mapping/vrs_map.py b/src/dcd_mapping/vrs_map.py
index ea2bf25..b36e043 100644
--- a/src/dcd_mapping/vrs_map.py
+++ b/src/dcd_mapping/vrs_map.py
@@ -32,7 +32,7 @@
     get_seqrepo,
     translate_hgvs_to_vrs,
 )
-from dcd_mapping.resource_utils import request_with_backoff
+from dcd_mapping.resource_utils import is_missing_value, request_with_backoff
 from dcd_mapping.schemas import (
     AlignmentResult,
     MappedScore,
@@ -378,7 +378,11 @@ def _map_protein_coding_pro(
     :param transcript: The transcript selection information for a score set
     :return: VRS mapping object if mapping succeeds
     """
-    if row.hgvs_pro in {"_wt", "_sy", "NA"} or len(row.hgvs_pro) == 3:
+    if (
+        row.hgvs_pro in {"_wt", "_sy"}
+        or is_missing_value(row.hgvs_pro)
+        or len(row.hgvs_pro) == 3
+    ):
         _logger.warning(
             "Can't process variant syntax %s for %s", row.hgvs_pro, row.accession
         )
@@ -700,7 +704,7 @@ def _hgvs_nt_is_valid(hgvs_nt: str) -> bool:
     :return: True if expression appears populated and valid
     """
     return (
-        (hgvs_nt != "NA")
+        (not is_missing_value(hgvs_nt))
         and (hgvs_nt not in {"_wt", "_sy", "="})
         and (len(hgvs_nt) != 3)
     )
@@ -713,7 +717,8 @@ def _hgvs_pro_is_valid(hgvs_pro: str) -> bool:
     :return: True if expression appears populated and valid
     """
     return (
-        (hgvs_pro not in {"_wt", "_sy", "NA"})
+        (hgvs_pro not in {"_wt", "_sy"})
+        and (not is_missing_value(hgvs_pro))
         and (len(hgvs_pro) != 3)
         and ("fs" not in hgvs_pro)
     )