M31.0 classifies hypersensitivity angiitis, an immune-mediated necrotizing vasculopathy of small vessels, and explicitly includes Goodpasture's syndrome (anti-glomerular basement membrane disease) as an applicable condition under this code.

Documentation tips

What should appear in the chart to support M31.0.

Source · Editorial brief grounded in 7 cited references ↓

• Provider must explicitly document 'hypersensitivity angiitis,' 'Goodpasture's syndrome,' or 'anti-GBM disease' — a generic 'vasculitis' or 'angiitis NOS' is insufficient and will land on a less-specific code.
• For Goodpasture's syndrome, confirm the record contains serological findings (anti-GBM antibody titer) and/or biopsy results showing linear IgG deposition along the glomerular basement membrane to defend M31.0 on audit.
• Document organ involvement explicitly (renal, pulmonary, or both) — additional codes for glomerulonephritis or pulmonary hemorrhage may be appropriate if those manifestations are not considered integral to the syndrome.
• If the diagnosis is still under investigation (suspected, possible, rule out), follow outpatient coding guidelines and code the presenting signs or symptoms rather than M31.0 until the diagnosis is confirmed.
• Note any trigger or antigen exposure (drug, infection, foreign substance) in the clinical note — this supports the hypersensitivity mechanism and reinforces M31.0 over other vasculitis codes.

Related CPT procedures

Procedure codes commonly billed with M31.0. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

Common coding pitfalls

The recurring mistakes coders make with M31.0 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Coding to the non-billable parent M31 (Other necrotizing vasculopathies) instead of the specific billable M31.0 — claims submitted with M31 will reject.
• Using I77.6 (Arteritis, unspecified) when the record clearly documents hypersensitivity angiitis — I77.6 is excluded from the M30–M36 block by a Type 2 Excludes note, meaning M31.0 is the correct home when the condition falls within systemic connective tissue disorders.
• Conflating leukocytoclastic cutaneous vasculitis with hypersensitivity angiitis without a provider diagnosis — these share clinical features but require distinct provider documentation to support M31.0.
• Assigning M31.0 for Goodpasture's syndrome based on lab findings alone without a physician-documented diagnosis — code assignment requires provider attestation, not coder interpretation of lab values.
• Failing to code co-existing organ-specific manifestations (e.g., glomerulonephritis, pulmonary hemorrhage) when those conditions are documented and not considered integral to the syndrome per facility guidelines.

Clinical context

Source · Editorial summary grounded in 7 cited references ↓

Inclusion & exclusion notes

Per the official ICD-10-CM Tabular List.

Source · CDC ICD-10-CM Official Tabular List · 2026

Sibling codes

Other billable codes under M31 (laterality / anatomic variants).