M31.7 ICD-10-CM Code: Microscopic polyangiitis
M31.7 maps to CMS-HCC V28 94. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · free HCC 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)
M31.7
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMicroscopic polyangiitis
A rare autoimmune condition where small blood vessels become inflamed and damaged, causing tissue injury throughout the body.
Buddy Insight
Microscopic polyangiitis is a necrotizing small vessel vasculitis that primarily affects kidneys and lungs, with high risk of organ failure and death if untreated.
CMS-HCC V28
MappedHCC 94
Code-level coefficient reference
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 056
Code-level coefficient reference
ESRD/PACE
MappedHCC 40
Code-level coefficient reference
RXHCC
MappedHCC 84
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Microscopic polyarteritis
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M31.7 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M31.7 in this effective period.
Excludes 1
Official- polyarteritis nodosa (M30.0)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M31.7 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M31.7 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M31.7 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 M31.7 an HCC code?
Yes. M31.7 (Microscopic polyangiitis) maps to HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.268. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: M31.7 is billable and maps to V28 HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M31.7
- Description
- Microscopic polyangiitis
- HCC (V28)
- HCC 94 — Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders
- RAF reference coefficient
- 0.268
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work M31.7 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT Criteria for M31.7
For M31.7 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 M31.7 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
M31.7 is the ICD-10-CM diagnosis code for microscopic polyangiitis. A rare autoimmune condition where small blood vessels become inflamed and damaged, causing tissue injury throughout the body. M31.7 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, M31.7 maps to Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders (HCC 94) with a source-labeled community, non-dual, aged reference coefficient of 0.268. No V24 mapping is shown for M31.7; use the applicable model and payment year when reviewing the V28 mapping. 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. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Use M31.7 when the provider wording supports microscopic polyangiitis. Check the FY2026 tabular notes and the full code path before the final code choice. Because M31.7 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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, source-labeled coefficient references, and MEAT documentation criteria for M31.7 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use M31.7 when the provider wording supports microscopic polyangiitis. Check the FY2026 tabular notes and the full code path before the final code choice.
- •For this DOS, capture the provider's current assessment and the care action documented for microscopic polyangiitis. Keep the checklist tied to the note.
- •Do not swap M31.7 with M31.0. The FY2026 tabular describes M31.0 as hypersensitivity angiitis. Follow the documented detail.
- •M31.7 maps to V28 HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders. The mapping does not replace the documentation review. The code still has to match the note.
- •Ask Buddy to show the official notes for M31.7 or compare its code path with M31.0.
Clinical Significance
Microscopic polyangiitis is a necrotizing small vessel vasculitis that primarily affects kidneys and lungs, with high risk of organ failure and death if untreated. Early recognition and aggressive immunosuppressive therapy are essential for preserving organ function.
Documentation Requirements
- ✓Clinical evidence of small vessel necrotizing vasculitis
- ✓Renal involvement with glomerulonephritis
- ✓Pulmonary involvement if present
- ✓ANCA testing (typically p-ANCA/MPO positive)
- ✓Biopsy confirmation from affected organs
- ✓Assessment of organ function
- ✓Treatment response monitoring
- ✓Long-term renal and pulmonary function tracking
Excludes 1, Do NOT code together
- polyarteritis nodosa (M30.0)
Commonly Confused Codes
- •M31.30: Wegener's granulomatosis without renal involvement (different ANCA-associated vasculitis)
- •M30.0: Polyarteritis nodosa (medium vessel involvement)
- •N05.9: Unspecified nephritic syndrome (isolated renal disease)
- •J84.10: Pulmonary fibrosis, unspecified (isolated lung disease)
- •M31.1: Thrombotic microangiopathy (different microvascular process)