2026 ICD-10-CM Diagnosis Code M31.11Hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]
ICD-10-CM Codes›M00–M99›M30-M36›M31
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 454
- Chronic Condition
M31.11 is a billable ICD-10-CM diagnosis code for hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 545 through 547. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 25 closely related codes. Coders also document this condition as thrombotic microangiopathy following transplantation of hematopoietic stem cell. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complication of transplanted organs or tissue, initial encounter; Systemic lupus erythematosus and connective tissue disorders; and Vasculitis.
For Medicare Advantage risk adjustment, M31.11 maps to CMS-HCC Category 454 (Stem Cell, Including Bone Marrow, Transplant Status/Complications) under the V28 model, adding a risk factor of about 1.068 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M31.11 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Thrombotic microangiopathy following transplantation of hematopoietic stem cell
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Transplant-associated thrombotic microangiopathy [TA-TMA]
Code First
- if applicable:
- complications of bone marrow transplant T86.0
- complications of stem cell transplant T86.5
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
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Code History & ChangesHistory
Replacement M31.11 replaces the following previously assigned code(s):
- M31.1 - Thrombotic microangiopathy
Questions About M31.11Overview
Is M31.11 (Thrombotic microangiopathy) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA] on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M31.11 group to?
When hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA] is the principal diagnosis on an inpatient stay, it groups to MS-DRG 545, 546, 547, with relative weights from 0.8362 to 2.4817 depending on complications. Higher weights mean higher Medicare reimbursement.
Is M31.11 a CC or MCC?
CMS lists M31.11 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 25 closely related codes in its exclusion list.
What HCC is M31.11?
M31.11 (hematopoietic stem cell transplantation-associated thrombotic microangiopathy [HSCT-TMA]) maps to CMS-HCC Category 454 (Stem Cell, Including Bone Marrow, Transplant Status/Complications), commonly written as HCC 454, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 186 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 395.
Does M31.11 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M31.11 adds a risk adjustment factor of about 1.068 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.416 to 1.596 depending on the payment segment). HCC 454 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 454 category page.
