D46.Z
BillableOther myelodysplastic syndromes
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D46.Z an HCC code?
Yes. D46.Z maps to Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Severe Hematological Disorders under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for D46.Z
For D46.Zto count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed D46.Z during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D46.Z is the ICD-10-CM diagnosis code for other myelodysplastic syndromes. A bone marrow disorder where blood cells develop abnormally, but the specific type doesn't fit into other defined categories. D46.Z sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (d37-d48).
Under the CMS-HCC V28 risk adjustment model, D46.Z maps to Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers (HCC 19) with a community, non-dual, aged base RAF weight of 1.798. Under the older CMS-HCC V24 model, D46.Z maps to Severe Hematological Disorders (HCC 46) with a community, non-dual, aged base RAF weight of 1.372. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Use this code only when the myelodysplastic syndrome doesn't meet criteria for more specific subtypes (A, B, or C). Because D46.Z maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for D46.Z sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the myelodysplastic syndrome doesn't meet criteria for more specific subtypes (A, B, or C)
- •Document the specific characteristics and any cytogenetic findings that distinguish it from other MDS types
Clinical Significance
This code captures myelodysplastic syndrome subtypes that do not fit into other defined categories (D46.0-D46.C), including rare or atypical variants. These patients still face the hallmark risks of myelodysplastic syndromes including progressive cytopenias, transfusion dependence, and potential transformation to acute myeloid leukemia.
Documentation Requirements
- ✓Documentation should include bone marrow biopsy findings, blast percentage, cytogenetic analysis, and the specific features that distinguish this case from other myelodysplastic syndrome categories.
- ✓Explain why the more specific D46 codes do not apply.
- ✓Document peripheral blood counts, transfusion history, and any treatment received.
Excludes 1 — Do NOT code together
- chronic myelomonocytic leukemia (C93.1-)
Commonly Confused Codes
- •D46.9 (myelodysplastic syndrome, unspecified) is used when the subtype is unknown, not when it is known but does not fit standard categories.
- •D46.0-D46.C are specific subtypes that should be assigned when criteria are met.
- •D47.1 (chronic myeloproliferative disease) may have overlapping features in myelodysplastic/myeloproliferative overlap syndromes.