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D46.C ICD-10-CM Code: Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality

D46.C maps to CMS-HCC V28 19. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools

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Code lookupD46.C

FY 2026 Apr update / Neoplasms (C00-D49) / Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (D37-D48)

D46.C

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality

A bone marrow disorder characterized by abnormal blood cell development with a specific chromosomal deletion (del 5q) that may respond better to certain treatments.

Buddy the Bee presenting code insight

Buddy Insight

Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality (also known as 5q- syndrome) is a distinct subtype characterized by macrocytic anemia, normal or elevated platelet counts, and hypolobated megakaryocytes.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 19

Coefficient HCC 19: 1.798 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 067

Code-level coefficient reference

ESRD/PACE

HCC 46

Code-level coefficient reference

RXHCC

HCC 16

Code-level coefficient reference

Code Book Path

Official
D46Myelodysplastic syndromesD46.CMyelodysplastic syndrome with isolated del(5q) chromosomal abnormality

Inclusion Terms

Official
  • Myelodysplastic syndrome with 5q deletion
  • 5q minus syndrome NOS

Excludes 2

Official
  • drug-induced aplastic anemia (D61.1)Inherited from D46

Related Codes

Official
D46.0Refractory anemia without ring sideroblasts, so statedD46.1Refractory anemia with ring sideroblastsD46.2Refractory anemia with excess of blasts [RAEB]D46.4Refractory anemia, unspecifiedD46.9Myelodysplastic syndrome, unspecified

Includes

Official

No Includes notes are included in this display for D46.C. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • neoplasms of unspecified behavior (D49.-)Inherited from D37-D48

Code First

Official

No Code First sequencing instructions are included in this display for D46.C. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)Inherited from D46

Code Also

Official

No Code Also instructions are included in this display for D46.C. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Documentation must include cytogenetic analysis showing isolated deletion of the long arm of chromosome 5 as the sole cytogenetic abnormality.
Bone marrow biopsy should demonstrate characteristic hypolobated megakaryocytes with blast percentage below 5%.
Document response to lenalidomide therapy if initiated.
Peripheral blood counts showing macrocytic anemia with normal or elevated platelets support the diagnosis.

MEAT Support

HCC Buddy guidance
Documentation must include cytogenetic analysis showing isolated deletion of the long arm of chromosome 5 as the sole cytogenetic abnormality.
Bone marrow biopsy should demonstrate characteristic hypolobated megakaryocytes with blast percentage below 5%.
Document response to lenalidomide therapy if initiated.
Peripheral blood counts showing macrocytic anemia with normal or elevated platelets support the diagnosis.

Audit Caution

HCC Buddy guidance
This code requires isolated del(5q) as the sole chromosomal abnormality
if additional cytogenetic changes are present, a different myelodysplastic syndrome code may be more appropriate. Lenalidomide is a specific treatment for this subtype, and its use should prompt consideration of this diagnosis. Ensure the blast count remains below 5% for this classification.

Common Mistakes

HCC Buddy guidance
D46.0 (refractory anemia without ring sideroblasts) lacks the specific cytogenetic finding.
D46.9 (myelodysplastic syndrome, unspecified) should not be used when del(5q) is documented.
D46.Z (other myelodysplastic syndromes) is for myelodysplastic syndromes that do not fit other specific categories.
If del(5q) is present with additional cytogenetic abnormalities, this code may not be appropriate.

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is D46.C an HCC code?

Yes. D46.C (Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality) maps to HCC 19, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.798. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: D46.C is billable and maps to V28 HCC 19, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
D46.C
Description
Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality
HCC (V28)
HCC 19 — Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers
RAF reference coefficient
1.798
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 19, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers
1.798
ESRDHCC 46, Severe Hematological Disorders
Not separately weighted
RxHCCHCC 16, Multiple Myeloma and Other Hematologic Cancers
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work D46.C in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D46.C

For D46.C, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

D46.C is the ICD-10-CM diagnosis code for myelodysplastic syndrome with isolated del(5q) chromosomal abnormality. A bone marrow disorder characterized by abnormal blood cell development with a specific chromosomal deletion (del 5q) that may respond better to certain treatments. D46.C 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.C maps to Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers (HCC 19) with a source-labeled community, non-dual, aged reference coefficient of 1.798. No V24 mapping is shown for D46.C; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Cytogenetic testing documentation showing del(5q) is essential for accurate coding of this subtype. For D46.C, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for D46.C sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Cytogenetic testing documentation showing del(5q) is essential for accurate coding of this subtype
  • •This subtype has a better prognosis and different treatment options; ensure cytogenetic results are in the medical record

Clinical Significance

Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality (also known as 5q- syndrome) is a distinct subtype characterized by macrocytic anemia, normal or elevated platelet counts, and hypolobated megakaryocytes. This subtype has a favorable prognosis with low risk of leukemic transformation and responds well to lenalidomide therapy, making accurate identification clinically important.

Documentation Requirements

  • ✓Documentation must include cytogenetic analysis showing isolated deletion of the long arm of chromosome 5 as the sole cytogenetic abnormality.
  • ✓Bone marrow biopsy should demonstrate characteristic hypolobated megakaryocytes with blast percentage below 5%.
  • ✓Document response to lenalidomide therapy if initiated.
  • ✓Peripheral blood counts showing macrocytic anemia with normal or elevated platelets support the diagnosis.

Commonly Confused Codes

  • •D46.0 (refractory anemia without ring sideroblasts) lacks the specific cytogenetic finding.
  • •D46.9 (myelodysplastic syndrome, unspecified) should not be used when del(5q) is documented.
  • •D46.Z (other myelodysplastic syndromes) is for myelodysplastic syndromes that do not fit other specific categories.
  • •If del(5q) is present with additional cytogenetic abnormalities, this code may not be appropriate.

Child Codes

D46.0Refractory anemia without ring sideroblasts, so stated
HCC 19
D46.1Refractory anemia with ring sideroblasts
HCC 19
D46.2Refractory anemia with excess of blasts [RAEB]
D46.4Refractory anemia, unspecified
HCC 19
D46.9Myelodysplastic syndrome, unspecified
HCC 19
D46.ARefractory cytopenia with multilineage dysplasia
HCC 19
D46.BRefractory cytopenia with multilineage dysplasia and ring sideroblasts
HCC 19
D46.CMyelodysplastic syndrome with isolated del(5q) chromosomal abnormality
HCC 19
D46.ZOther myelodysplastic syndromes
HCC 19

Code Hierarchy

└D46Myelodysplastic syndromes└D46.CMyelodysplastic syndrome with isolated del(5q) chromosomal abnormality
└D46.CMyelodysplastic syndrome with isolated del(5q) chromosomal abnormality

Also searched as

  • D46 C
  • D46C

For D46.C, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

D46.C maps to CMS-HCC V28 category 19, Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for D46.C. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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