2027 ICD-10-CM Diagnosis Code M31.8Other specified necrotizing vasculopathies
ICD-10-CM Codes›M00–M99›M30-M36›M31
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 94
- Chronic Condition
M31.8 is a billable ICD-10-CM diagnosis code for other specified necrotizing vasculopathies. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 299 through 301. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 3 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Systemic lupus erythematosus and connective tissue disorders and Vasculitis.
For Medicare Advantage risk adjustment, M31.8 maps to CMS-HCC Category 94 (Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders) under the V28 model, adding a risk factor of about 0.268 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M31.8 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 2027.
Source: CMS Payment Year 2027 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.
- Abnormal blood test
- Complement level below reference range
- Demyelination due to systemic vasculitis
- Drug-induced necrotizing vasculitis
- Hypersensitivity reaction mediated by immune complex
- Hypocomplementemic urticarial vasculitis
- Interstitial lung disease due to systemic disease
- Interstitial lung disease with systemic vasculitis
- Necrotizing vasculitis of undetermined etiology
- Necrotizing vasculitis secondary to connective tissue disease
- Necrotizing vasculitis secondary to infection
- Primary cutaneous vasculitis
- Primary necrotizing systemic vasculitis
- Rheumatoid necrotizing vasculitis
- Secondary cutaneous vasculitis
- Small vessel vasculitis caused by immune complex
- Systemic vasculitis
- Vasculitis due to systemic disease
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to M31.8: its own notes plus those printed at block M30-M36 and Chapter 13. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- autoimmune disease NOS
- collagen (vascular) disease NOS
- systemic autoimmune disease
- systemic collagen (vascular) disease
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Hypocomplementemic vasculitis
- Septic vasculitis
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- autoimmune disease, single organ or single cell-type -code to relevant condition category
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- arthropathic psoriasis (L40.5-)
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- compartment syndrome (traumatic) (T79.A-)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Notes
General instructions on how these codes are used.
- Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name M31.8, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming M31.8: they are not reported together with it, unless the two conditions are unrelated.
- L94 Other localized connective tissue disorders
Excludes2 4
These codes carry an Excludes2 note naming M31.8: its condition is not part of those codes, and both may be reported when the patient has both.
- Chapter 9 (I00-I99) Diseases of the circulatory system
- I77 Other disorders of arteries and arterioles
- J82 Pulmonary eosinophilia, not elsewhere classified
- Chapter 12 (L00-L99) Diseases of the skin and subcutaneous tissue
Code First 1
These codes say to code first a condition named in the note, and M31.8 is one of the conditions named.
- J84.170 Interstitial lung disease with progressive fibrotic phenotype in diseases classified elsewhere
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
hypocomplementemic M31.8
systemic M31.8
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Vasculitis
Vasculitis is an inflammation of the blood vessels. It happens when the body's immune system attacks the blood vessel by mistake. It can happen because of an infection, a medicine, or another disease. The cause is often unknown.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert M31.8 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M31.8Overview
What is the ICD-10 code for other specified necrotizing vasculopathies?
The ICD-10-CM code for other specified necrotizing vasculopathies is M31.8 (sometimes written as M318). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is M31.8 (Other necrotizing vasculopathies) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other specified necrotizing vasculopathies on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does M31.8 group to?
When other specified necrotizing vasculopathies is the principal diagnosis on an inpatient stay, it groups to MS-DRG 301, 300, 299, with relative weights from 0.7132 to 1.5840 depending on complications. Higher weights mean higher Medicare reimbursement.
Is M31.8 a CC or MCC?
CMS lists M31.8 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 3 closely related codes in its exclusion list.
What is the ICD-9 equivalent of M31.8?
Under the General Equivalence Mappings, other specified necrotizing vasculopathies converts to ICD-9-CM 447.5 (necrosis of artery). The mapping is approximate, so confirm the match fits the documentation.
What HCC is M31.8?
M31.8 (other specified necrotizing vasculopathies) maps to CMS-HCC Category 94 (Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders), commonly written as HCC 94, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 108 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does M31.8 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M31.8 adds a risk adjustment factor of about 0.268 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.196 to 0.297 depending on the payment segment). A more severe related category (HCC 93) supersedes it when both are reported. See the full factor table on the HCC 94 category page.
