MDS ICD-10 Codes 2026
Complete guide to ICD-10 codes for Myelodysplastic Syndromes. Master the D46 code family with WHO classification mapping, documentation requirements, and billing guidance.
Key Takeaways
- D46 is the primary code family for all Myelodysplastic Syndromes
- Bone marrow biopsy findings determine the specific code (blast %, ring sideroblasts, dysplasia)
- D46.C is specific for 5q deletion syndrome (isolated del(5q))
- ≥20% blasts = AML, not MDS (use C92.x codes instead)
Understanding Myelodysplastic Syndromes
Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis, peripheral blood cytopenias, and risk of transformation to acute myeloid leukemia (AML). Accurate ICD-10 coding is essential for proper reimbursement and clinical tracking.
Key Clinical Features
- • Cytopenias (anemia, thrombocytopenia, neutropenia)
- • Dysplastic changes in bone marrow cells
- • Increased blast percentage (but <20%)
- • Cytogenetic abnormalities
- • Risk of AML transformation
Diagnosis Requirements
- • Bone marrow aspiration and biopsy
- • Cytogenetic analysis (karyotype)
- • Iron staining (ring sideroblasts)
- • Flow cytometry
- • Molecular testing (SF3B1, TET2, etc.)
Complete D46 ICD-10 Code List
| ICD-10 Code | Description | Billable |
|---|---|---|
| Refractory Anemia Types | ||
| D46.0 | Refractory anemia without ring sideroblasts, so stated | Yes |
| D46.1 | Refractory anemia with ring sideroblasts (RARS) | Yes |
| Refractory Anemia with Excess Blasts (RAEB) | ||
| D46.2 | Refractory anemia with excess of blasts [RAEB] | No (use subcodes) |
| D46.20 | Refractory anemia with excess of blasts, unspecified | Yes |
| D46.21 | Refractory anemia with excess of blasts 1 (RAEB-1) | Yes |
| D46.22 | Refractory anemia with excess of blasts 2 (RAEB-2) | Yes |
| Multilineage Dysplasia | ||
| D46.A | Refractory cytopenia with multilineage dysplasia (RCMD) | Yes |
| D46.B | Refractory cytopenia with multilineage dysplasia and ring sideroblasts (RCMD-RS) | Yes |
| Specific Genetic Abnormalities | ||
| D46.C | Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality | Yes |
| Other & Unspecified | ||
| D46.4 | Refractory anemia, unspecified | Yes |
| D46.Z | Other myelodysplastic syndromes | Yes |
| D46.9 | Myelodysplastic syndrome, unspecified | Yes |
Coding Tip
Avoid D46.9 when possible. Unspecified codes may trigger medical necessity reviews and lower reimbursement. Always code to the highest specificity supported by documentation.
WHO Classification to ICD-10 Mapping
The WHO 2022 classification of MDS maps to ICD-10-CM codes as follows:
| WHO 2022 Classification | Key Features | ICD-10 Code |
|---|---|---|
| MDS with low blasts (MDS-LB) | <5% blasts, no Auer rods | D46.0, D46.A |
| MDS with low blasts and SF3B1 mutation (MDS-SF3B1) | SF3B1 mutation, ring sideroblasts | D46.1, D46.B |
| MDS with increased blasts-1 (MDS-IB1) | 5-9% blasts | D46.21 |
| MDS with increased blasts-2 (MDS-IB2) | 10-19% blasts or Auer rods | D46.22 |
| MDS with isolated 5q deletion | del(5q) as sole abnormality, <5% blasts | D46.C |
| MDS with biallelic TP53 inactivation | TP53 mutation, complex karyotype | D46.Z |
| Hypoplastic MDS | Hypocellular marrow (<30%) | D46.Z |
| MDS, NOS | Does not fit other categories | D46.9 |
How to Select the Right Code
Decision Tree for MDS Coding
Step 1: Check Blast Percentage
- • ≥20% blasts: This is AML, not MDS → Use C92.x codes
- • 10-19% blasts: → D46.22 (RAEB-2)
- • 5-9% blasts: → D46.21 (RAEB-1)
- • <5% blasts: → Continue to Step 2
Step 2: Check Cytogenetics
- • Isolated del(5q): → D46.C
- • Other abnormalities: → Continue to Step 3
Step 3: Check Ring Sideroblasts
- • ≥15% ring sideroblasts OR SF3B1 mutation:
- → Single lineage dysplasia: D46.1
- → Multilineage dysplasia: D46.B
- • <15% ring sideroblasts: → Continue to Step 4
Step 4: Check Dysplasia Type
- • Single lineage dysplasia: → D46.0
- • Multilineage dysplasia: → D46.A
- • Unspecified: → D46.9
Documentation Requirements
Required Documentation
- ✓ Bone marrow biopsy date and results
- ✓ Blast percentage (marrow and peripheral)
- ✓ Cytogenetic/karyotype findings
- ✓ Ring sideroblast percentage
- ✓ Number of dysplastic lineages
- ✓ WHO classification
- ✓ IPSS-R risk score (if available)
Supporting Documentation
- • CBC with differential
- • Reticulocyte count
- • Iron studies (ferritin, TIBC)
- • B12 and folate levels
- • Flow cytometry results
- • Molecular/NGS panel results
- • Transfusion history
Documentation Example
Diagnosis: Myelodysplastic syndrome with excess blasts-2 (MDS-EB2)
Bone marrow biopsy (12/15/2025):
- - Cellularity: 60% (normocellular)
- - Blast count: 15% (marrow), 8% (peripheral)
- - Dysplasia: Trilineage
- - Ring sideroblasts: 8%
Cytogenetics: 46,XY,del(7)(q22)[18]/46,XY[2]
IPSS-R: High risk (score 5.5)
ICD-10: D46.22 (Refractory anemia with excess of blasts 2)
Billing & Coding Tips
Best Practices
- ✓ Always code to highest specificity - D46.9 should be rare
- ✓ Update codes when disease progresses - RAEB-1 to RAEB-2, or MDS to AML
- ✓ Link secondary diagnoses - anemia, thrombocytopenia to MDS
- ✓ Document treatment rationale - supports medical necessity
- ✓ Include IPSS-R risk score - justifies treatment intensity
Common Coding Errors
- ✗ Using D46.9 when specific subtype is documented
- ✗ Continuing to code MDS after AML transformation
- ✗ Missing ring sideroblast percentage (D46.1 vs D46.0)
- ✗ Not coding 5q deletion syndrome specifically (use D46.C)
- ✗ Failing to update codes when blast count changes
Common MDS Treatments & Coding
- • Azacitidine (Vidaza): Z51.11 + MDS code
- • Decitabine (Dacogen): Z51.11 + MDS code
- • Lenalidomide (Revlimid) for 5q-: Z51.11 + D46.C
- • Luspatercept (Reblozyl): Z51.12 + MDS code
- • Transfusion support: Include D64.x for anemia
Frequently Asked Questions
What is the ICD-10 code for myelodysplastic syndrome?
MDS uses codes from the D46 family. D46.9 (Myelodysplastic syndrome, unspecified) is the general code, but specific subtypes should use D46.0 (RA), D46.1 (RARS), D46.20-D46.22 (RAEB), D46.A (RCMD), D46.B (RCMD-RS), or D46.C (MDS with 5q deletion).
What is the difference between D46.0 and D46.1?
D46.0 is for Refractory Anemia (RA) without ring sideroblasts. D46.1 is for Refractory Anemia with Ring Sideroblasts (RARS/MDS-RS), which requires ≥15% ring sideroblasts on bone marrow examination or SF3B1 mutation.
How do I code MDS with excess blasts?
MDS with excess blasts uses D46.20 (RAEB, unspecified), D46.21 (RAEB-1 with 5-9% blasts), or D46.22 (RAEB-2 with 10-19% blasts). The blast percentage from bone marrow biopsy determines the specific code.
What documentation is required for MDS coding?
MDS coding requires bone marrow biopsy results showing blast percentage, cytogenetic findings (especially 5q deletion), ring sideroblast percentage, and dysplasia type (single vs. multilineage). WHO classification and IPSS-R risk score should be documented.
What is the ICD-10 code for MDS 5q deletion syndrome?
D46.C is the specific code for Myelodysplastic syndrome with isolated del(5q) chromosomal abnormality. This is also known as 5q- syndrome and typically presents with macrocytic anemia and normal or high platelet counts.
Can MDS transform to leukemia and how do I code that?
Yes, MDS can transform to Acute Myeloid Leukemia (AML) when blast count reaches ≥20%. Once transformed, use AML codes (C92.x) instead of MDS codes. History of MDS can be captured with Z85.6 (personal history of leukemia).
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