M35.6 classifies relapsing panniculitis of the Weber-Christian type — a systemic connective tissue disorder characterized by recurring episodes of inflammation in subcutaneous and, in some cases, visceral adipose tissue, presenting with painful nodules, erythema, fever, and myalgia.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 5
- Region
- General
Documentation tips
What should appear in the chart to support M35.6.
Source · Editorial brief grounded in 4 cited references ↓
- Explicitly document the relapsing pattern — note the number of episodes and the interval (weeks or months) between flares, since the 'relapsing' qualifier is what separates M35.6 from M79.3.
- Record all systemic features present during the episode: fever, myalgia, fatigue, or internal organ involvement, to substantiate the systemic connective tissue disorder classification.
- If a skin biopsy was performed, document the pathology result — lobular panniculitis with or without vasculitis — and link the biopsy finding explicitly to the clinical diagnosis in the assessment.
- Distinguish the causative or associated condition: if lupus is the driver, document it separately so the coder can evaluate whether L93.2 supersedes M35.6.
- Note all body sites affected by nodules (thighs, trunk, extremities, mesentery) to support medical necessity for any imaging or additional workup coded alongside M35.6.
Related CPT procedures
Procedure codes commonly billed with M35.6. 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 M35.6 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M79.3 (Panniculitis NOS) when the provider has clearly documented the relapsing Weber-Christian pattern — M35.6 is the required code and M79.3 is Excludes1 in this context.
- Assigning M35.6 when the panniculitis is attributable to lupus erythematosus — L93.2 is the correct code for lupus panniculitis and is an Excludes1 conflict with M35.6.
- Failing to distinguish M35.6 from neck and back panniculitis (M54.0-), which is separately classified and should be coded to that subcategory when panniculitis is localized to the spine region.
- Appending a 7th-character extension to M35.6 — this code has no 7th-character requirement and no laterality subdivisions; adding one creates an invalid code.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
Weber-Christian disease (M35.6) sits within the systemic connective tissue disorders block (M30–M36), not under general panniculitis (M79.3). That distinction matters at audit: M79.3 is explicitly excluded when the relapsing, systemic nature of the condition is documented. Use M35.6 only when the provider documents a relapsing pattern — episodic recurrence over weeks or months — often accompanied by systemic features such as fever, malaise, or organ involvement beyond the skin.
The code carries two hard Excludes1 relationships: lupus panniculitis (L93.2) and panniculitis NOS (M79.3). If the attending has documented an underlying connective tissue disease such as lupus as the driver of the panniculitis, pivot to L93.2. If the provider documents nodular nonsuppurative panniculitis without confirming the relapsing Weber-Christian pattern, use M79.3 instead. When systemic connective tissue disease is confirmed and panniculitis is a manifestation, sequence accordingly per the Tabular conventions.
M35.6 has no laterality subdivisions and no 7th-character extensions — it is a single billable code. In an orthopedic or rheumatology practice, this code most commonly surfaces when a rheumatologist is managing a patient with systemic connective tissue involvement, or when joint/soft tissue complaints prompt workup that reveals the panniculitis diagnosis. Document the relapsing episode count, affected sites, systemic symptoms, and any biopsy confirmation to satisfy clinical validation requirements.
Inclusion & exclusion notes
Per the official ICD-10-CM Tabular List.
Source · CDC ICD-10-CM Official Tabular List · 2026
Excludes 1 — never code together
- lupus panniculitis (L93.2)
- panniculitis NOS (M79.3-)
Sibling codes
Other billable codes under M35 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What is the difference between M35.6 and M79.3?
02Can M35.6 and L93.2 be coded together?
03Does M35.6 require a laterality digit or 7th character?
04What documentation is required to support M35.6 over an unspecified panniculitis code?
05Is M35.6 appropriate when panniculitis affects the neck or back?
06In what specialty settings does M35.6 most commonly appear?
07What CPT codes typically accompany M35.6 on a claim?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (FY2026, effective Oct 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M30-M36/M35-/M35.6
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M35.6
- 04cms.govhttps://www.cms.gov/files/document/fy-2026-icd-10-cm-coding-guidelines.pdf
Mira AI Scribe
The Mira AI Scribe captures the relapsing episode pattern (frequency, interval), systemic symptoms (fever, myalgia, organ involvement), affected anatomic sites, and any biopsy or imaging findings from the encounter note — the clinical detail that separates billable M35.6 from the less-specific M79.3 and prevents a payer downcode or medical-necessity denial.
See how Mira captures M35.6 documentation