M31.7 Microscopic polyangiitis

ICD-10-CM Diagnosis Code M31.7: Microscopic Polyangiitis

ICD-10-CM code M31.7 represents microscopic polyangiitis, a small vessel necrotizing vasculitis classified within antineutrophil cytoplasmic antibody-associated vasculitides. The active terminology record is nested under other necrotizing vasculopathies. It excludes polyarteritis nodosa, distinguishing it from related inflammatory conditions. 1 2 4

Plain-language overview

Microscopic polyangiitis is a small vessel necrotizing vasculitis that exists within a broader group of disorders known as antineutrophil cytoplasmic antibody-associated vasculitides. 2

Historical literature originally described microscopic polyangiitis as microscopic polyarteritis in 1948 to characterize a specific pattern of glomerulonephritis observed in polyarteritis nodosa patients. 2

What this code represents

The ICD-10-CM terminology record assigns code M31.7 the preferred name microscopic polyangiitis, classifies its semantic type as a disease or syndrome, and maintains an active status. 1

Code M31.7 includes the synonym microscopic polyarteritis and carries an excludes one note for polyarteritis nodosa, which is coded separately as M30.0. 4

Coding details

In the ICD-10-CM hierarchy, M31.7 falls under chapter thirteen for diseases of the musculoskeletal system, specifically within the M30 to M36 block and the parent category M31. 5

The parent concept for M31.7 is M31, titled other necrotizing vasculopathies, and the terminology record indicates that M31.7 possesses narrower concepts within the system. 1

Documentation considerations

Clinical documentation for microscopic polyangiitis involves identifying early signs to facilitate timely diagnosis, selecting appropriate diagnostic tests for organ involvement, and implementing evidence-based induction and maintenance therapies. 2

What the sources add

While the clinical reference defines microscopic polyangiitis as an inflammatory, necrotizing condition, the official ICD-10-CM record establishes the exact code M31.7 and its active disease classification. 1 3

Coding sources list M31.7 alongside related but distinct conditions like Wegener's granulomatosis and hypersensitivity angiitis, while explicitly separating it from polyarteritis nodosa through an exclusion note. 4 6

Sources

1. ICD-10-CM M31.7 terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. Bookshelf — ncbi.nlm.nih.gov; accessed 2026-07-27.
3. Ontology Lookup Service (OLS) — purl.obolibrary.org; accessed 2026-07-27.
4. Coding: ICD-10-CM Section M30-M36 — medicalcodecenter.com; accessed 2026-07-27.
5. M31.7 — medcode.ch; accessed 2026-07-27.
6. ICD-10-CM 2024 | M31.3 - Wegener's granulomatosis — unboundmedicine.com; accessed 2026-07-27.