M31.5 identifies giant cell arteritis (GCA) occurring concurrently with polymyalgia rheumatica (PMR) — a combined presentation requiring documentation of both conditions to justify this code over M31.6.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 0
- Region
- Other
Documentation tips
What should appear in the chart to support M31.5.
Source · Editorial brief grounded in 5 cited references ↓
- Explicitly name both diagnoses — 'giant cell arteritis' AND 'polymyalgia rheumatica' — in the assessment; a single mention of GCA alone defaults the code to M31.6.
- Record inflammatory marker values (ESR and/or CRP) at the time of diagnosis; these are clinical validation requirements for M31.5 and support medical necessity on audit.
- Document biopsy results (temporal artery biopsy) or imaging findings (e.g., PET-CT, duplex ultrasound) that confirm GCA — pathology or radiology reports should be linked to the encounter.
- Note patient age (≥50 is the expected demographic); a GCA diagnosis in a patient under 50 should prompt additional documentation explaining the atypical presentation.
- If vision changes are present, add H53.9 (Unspecified visual disturbance) as a secondary code; this flags ischemic ophthalmic risk and supports urgency of treatment documentation.
- Document corticosteroid therapy initiation — medication and dose — as it is both standard of care and an indicator that the diagnosis has been clinically confirmed.
Common coding pitfalls
The recurring mistakes coders make with M31.5 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M31.6 when PMR is documented: if the note explicitly states PMR coexists with GCA, M31.6 is incorrect — M31.5 is the required code.
- Adding M35.3 alongside M31.5: M35.3 carries an Excludes1 note for 'polymyalgia rheumatica with giant cell arteritis (M31.5),' making the two codes mutually exclusive in standard ICD-10-CM usage; review payer rules before appending M35.3.
- Coding M31.5 without documented PMR symptoms: if the note mentions only GCA with no PMR language, M31.5 is not supported — use M31.6 and query the provider if clinically unclear.
- Omitting secondary symptom codes for vision disturbance or headache: these associated findings (H53.9, R51.9) add clinical specificity and support the severity reflected in the record.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
M31.5 is the correct code when the treating clinician explicitly documents both giant cell arteritis and polymyalgia rheumatica in the same encounter. GCA is a granulomatous inflammation of medium- and large-caliber arteries — most often the temporal arteries — typically presenting in patients aged 50 or older with headache, jaw claudication, scalp tenderness, and elevated inflammatory markers (ESR ≥50 mm/hr or CRP ≥10 mg/dL). PMR presents alongside GCA in a significant subset of patients, characterized by proximal girdle pain and stiffness affecting the shoulders, neck, and hips. When both are documented, M31.5 captures the full clinical picture in a single billable code.
Do not use M31.5 if PMR is absent or undocumented — drop to M31.6 (Other giant cell arteritis) instead. Conversely, do not use M35.3 (Polymyalgia rheumatica) when GCA is also documented; M35.3 carries an Excludes1 note pointing to M31.5, meaning the two codes cannot be reported together for the same condition. If PMR symptoms need separate tracking, some sources note M35.3 as a potential ancillary code, but the Excludes1 relationship means coders must review payer-specific guidance before adding it alongside M31.5.
Clinical validation requirements for M31.5 include: documented symptoms of both GCA (cranial or ischemic symptoms) and PMR (proximal muscle pain/stiffness), elevated ESR or CRP, and biopsy or imaging evidence supporting the GCA diagnosis. Corticosteroid initiation (typically high-dose prednisone) is the standard treatment response and should be reflected in medication reconciliation if used to support medical necessity.
Sibling codes
Other billable codes under M31 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01What is the difference between M31.5 and M31.6?
02Can I code M35.3 and M31.5 together on the same claim?
03Does M31.5 require a temporal artery biopsy to be coded?
04Is M31.5 age-restricted?
05What secondary codes pair with M31.5?
06Does M31.5 use a 7th-character extension?
07What if the patient has GCA confirmed but PMR is only suspected — which code applies?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M30-M36/M31-/M31.5
- 03icdcodes.aihttps://icdcodes.ai/diagnosis/giant-cell-arteritis/documentation
- 04aapc.comhttps://www.aapc.com/codes/icd-10-codes/M31.5
- 05pmc.ncbi.nlm.nih.govhttps://pmc.ncbi.nlm.nih.gov/articles/PMC7367731/
Mira AI Scribe
The Mira AI Scribe captures documentation of both GCA and PMR symptom sets — cranial symptoms (headache, jaw claudication, scalp tenderness), proximal girdle pain/stiffness, laboratory values (ESR, CRP), and biopsy or imaging findings — from the encounter note. This prevents downcoding to M31.6 or an incorrect split between M31.5 and M35.3, and ensures the record satisfies clinical validation requirements on payer audit.
See how Mira captures M31.5 documentation