2026 ICD-10-CM Diagnosis Code M31.7Microscopic polyangiitis
ICD-10-CM Codes›M00–M99›M30-M36›M31
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 94
- Chronic Condition
M31.7 is a billable ICD-10-CM diagnosis code for microscopic polyangiitis. 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 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 77 closely related codes. Coders also document this condition as disorder of respiratory system due to microscopic polyangiitis. 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, M31.7 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 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M31.7 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.
- Disorder of respiratory system due to microscopic polyangiitis
- Microscopic polyangiitis
- Necrosis of artery
- Polyarteritis
- Vasculitis due to systemic disease
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Microscopic polyarteritis
Type 1 Excludes
- polyarteritis nodosa M30.0
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.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disorder (of) See Also: Disease;
Glomerulonephritis See Also: Nephritis; N05.9
microscopic M31.7
microscopic M31.7
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Microscopic Polyangiitis
a primary systemic vasculitis of small- and some medium-sized vessels. it is characterized by a tropism for kidneys and lungs, positive association with anti-neutrophil cytoplasmic antibodies (anca), and a paucity of immunoglobulin deposits in vessel walls.
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 M31.7 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M31.7Overview
What is the ICD-10 code for microscopic polyangiitis?
The ICD-10-CM code for microscopic polyangiitis is M31.7 (sometimes written as M317). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is M31.7 (Other necrotizing vasculopathies) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report microscopic polyangiitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M31.7 group to?
When microscopic polyangiitis 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 M31.7 a CC or MCC?
CMS lists M31.7 as a CC (complication or comorbidity) for FY 2026. 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 77 closely related codes in its exclusion list.
What is the ICD-9 equivalent of M31.7?
Under the General Equivalence Mappings, microscopic polyangiitis converts to ICD-9-CM 446.0 (polyarteritis nodosa). The mapping is approximate, so confirm the match fits the documentation.
What HCC is M31.7?
M31.7 (microscopic polyangiitis) 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 2026. It mapped to HCC 40 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 84.
Does M31.7 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M31.7 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.
