M31.11 ICD-10-CM Code: Hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]
M31.11 maps to CMS-HCC V28 454 (RAF 1.068). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Systemic connective tissue disorders (M30-M36)
M31.11
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceHematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]
A serious complication that can occur after bone marrow or stem cell transplantation, where small blood vessels become blocked by clots.
Buddy Insight
HSCT-associated thrombotic microangiopathy is a serious complication of stem cell transplantation with high mortality risk.
CMS-HCC V28
MappedHCC 454
RAF 1.068
CMS-HCC V24
MappedHCC 186
RAF 0.832
ACA/HHS
MappedHCC 251
Varies by metal level
ESRD/PACE
MappedHCC 186
RAF 0.138
RXHCC
MappedHCC 395
RAF 4.379
Code Book Path
Inclusion Terms
Official- Transplant-associated thrombotic microangiopathy [TA-TMA]
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M31.11 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M31.11 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M31.11 in this effective period.
Code First
Official- if applicable:
- complications of bone marrow transplant (T86.0-)
- complications of stem cell transplant (T86.5)
Use Additional
Official- code to identify specific organ dysfunction, such as:
- acute kidney failure (N17.-)
- acute respiratory distress syndrome (J80)
- capillary leak syndrome (I78.8)
- diffuse alveolar hemorrhage (R04.89)
Code Also
OfficialICD-10-CM does not list Code Also instructions for M31.11 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 M31.11 an HCC code?
Yes. M31.11 (Hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]) maps to Stem Cell, Including Bone Marrow, Transplant Status/Complications under the CMS-HCC V28 risk adjustment model (and Major Organ Transplant or Replacement Status under V24), with a community non-dual aged RAF of 1.068. It is billable for payment year 2026.
Coder answer: M31.11 is billable and maps to V28 HCC 454, Stem Cell, Including Bone Marrow, Transplant Status/Complications. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M31.11
- Description
- Hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]
- HCC (V28)
- HCC 454 — Stem Cell, Including Bone Marrow, Transplant Status/Complications
- RAF
- 1.068
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so 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 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.
Work M31.11 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for M31.11
For M31.11 to 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 M31.11 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
M31.11 is the ICD-10-CM diagnosis code for hematopoietic stem cell transplantation-associated thrombotic microangiopathy [hsct-tma]. A serious complication that can occur after bone marrow or stem cell transplantation, where small blood vessels become blocked by clots. M31.11 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering systemic connective tissue disorders (m30-m36).
Under the CMS-HCC V28 risk adjustment model, M31.11 maps to Stem Cell, Including Bone Marrow, Transplant Status/Complications (HCC 454) with a community, non-dual, aged base RAF weight of 1.068. Under the older CMS-HCC V24 model, M31.11 maps to Major Organ Transplant or Replacement Status (HCC 186) with a community, non-dual, aged base RAF weight of 0.832. 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.
Always link this code to the transplant procedure code. Because M31.11 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 M31.11 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always link this code to the transplant procedure code
- •Document the timeframe of onset relative to the HSCT procedure
Clinical Significance
HSCT-associated thrombotic microangiopathy is a serious complication of stem cell transplantation with high mortality risk. This condition requires immediate recognition and aggressive management, as it can lead to multi-organ failure in already immunocompromised transplant recipients.
Documentation Requirements
- ✓Documentation of prior hematopoietic stem cell transplant
- ✓Timeline showing TMA onset post-transplant
- ✓Clinical evidence of microangiopathic hemolytic anemia
- ✓Thrombocytopenia in transplant setting
- ✓Organ dysfunction assessment
- ✓Exclusion of other TMA causes
- ✓GVHD status documentation
- ✓Treatment modifications for transplant setting
Use Additional Code
- code to identify specific organ dysfunction, such as:
- acute kidney failure (N17.-)
- acute respiratory distress syndrome (J80)
- capillary leak syndrome (I78.8)
- diffuse alveolar hemorrhage (R04.89)
- encephalopathy (metabolic) (septic) (G93.41)
- fluid overload, unspecified (E87.70)
- graft versus host disease (D89.81-)
- hemolytic uremic syndrome (D59.3-)
- hepatic failure (K72.-)
- hepatic veno-occlusive disease (K76.5)
- idiopathic interstitial pneumonia (J84.11-)
- sinusoidal obstruction syndrome (K76.5)
Code First
Commonly Confused Codes
- •M31.10: Thrombotic microangiopathy, unspecified (when transplant history not coded)
- •T86.01: Bone marrow transplant rejection (different transplant complication)
- •D89.813: Graft-versus-host disease, acute (different transplant complication)
- •D59.3: Hemolytic-uremic syndrome (not transplant-related)
- •Z94.81: Bone marrow transplant status (status code only)