M35.89

M35.89 captures systemic connective tissue disorders that are definitively diagnosed but do not fit any more specific code in the M30–M36 range — a true 'other specified' bucket for conditions such as eosinophilia-myalgia syndrome and collagen vascular disease NOS.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 5
Region: General

Drawn from CDCICD10DataAAPCCMS

Documentation tips

What should appear in the chart to support M35.89.

Source · Editorial brief grounded in 5 cited references ↓

Name the specific connective tissue disorder in the note — 'eosinophilia-myalgia syndrome' or 'collagen vascular disease' — rather than writing only 'CTD' or 'connective tissue disorder'; NOS/NEC language must still reflect a confirmed diagnosis, not a suspected one.
State that the condition is systemic in scope; localized connective tissue findings are coded elsewhere and will not support M35.89 on audit review.
When M35.89 accompanies a surgical episode, document how the connective tissue disorder affects perioperative risk, wound healing, or implant selection — this narrative supports medical necessity and justifies CC/MCC capture in DRG assignment.
If the disorder is post-COVID in origin and meets MIS criteria, do not use M35.89 — use M35.81 with U09.9 per official CMS coding guidelines.
Record any laboratory or diagnostic findings (e.g., elevated inflammatory markers, muscle enzyme levels, biopsy results) that confirm the diagnosis; vague documentation without objective support is the primary audit trigger for 'other specified' codes.

Related CPT procedures

Procedure codes commonly billed with M35.89. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

99213 $95.19

Established patient office or outpatient visit requiring 20–29 minutes of total time or low-complexity medical decision-making.

99214 $135.61

Office visit for an established patient requiring moderate-complexity medical decision making (MDM), or 30–39 minutes of total provider time on the date of service.

99215 $192.39

Highest-level office or outpatient E/M visit for an established patient, qualifying via high-complexity medical decision making or 40–54 minutes of total provider time on the date of service.

27447 $1,159.35

Knee replacement surgery addressing both the medial and lateral tibiofemoral compartments, with or without resurfacing of the patella.

27130 $1,162.02

Primary total hip arthroplasty replacing both the acetabular socket and proximal femoral components with prosthetic implants, with or without bone graft.

Common coding pitfalls

The recurring mistakes coders make with M35.89 and adjacent codes.

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

Assigning M35.89 for a suspected or probable connective tissue disorder — 'other specified' still requires a confirmed diagnosis; use sign/symptom codes (e.g., M79.3 for panniculitis, M79.89 for other soft-tissue disorders) until the diagnosis is established.
Defaulting to M35.89 when a more specific code exists — M35.81 (multisystem inflammatory syndrome), M35.1 (mixed CTD), and M35.00–M35.09 (Sjögren) each preempt M35.89; always check sibling codes before landing here.
Confusing M35.89 with M35.9 (unspecified systemic involvement of connective tissue) — M35.89 requires a named condition that lacks its own code; M35.9 is for truly uncharacterized disease.
Coding M35.89 alongside L87.1 (reactive perforating collagenosis), which is prohibited by the Excludes1 note at the M35 category level.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Use M35.89 when the physician documents a systemic connective tissue disorder that is confirmed and named, yet no more granular ICD-10-CM code exists for it. The Alphabetic Index routes eosinophilia-myalgia syndrome and 'collagen vascular disease NOS, specified NEC' directly here. If the condition is entirely unnamed or unspecified, drop to M35.9 instead.

In orthopedic settings, M35.89 most often appears as a secondary diagnosis — flagging a systemic connective tissue condition that complicates surgical planning, anesthesia risk stratification, or post-operative healing for joint replacement or soft-tissue repair patients. It lands in MS-DRG v43.0 groups 545 (with MCC), 546 (with CC), or 547 (without CC/MCC), so accurate complication/comorbidity coding alongside M35.89 directly affects DRG weight.

Do not use M35.89 for conditions with their own dedicated code: mixed connective tissue disease (M35.1), Sjögren syndrome (M35.00–M35.09), sicca syndrome, or multisystem inflammatory syndrome (M35.81). The parent category M35 carries an Excludes1 for reactive perforating collagenosis (L87.1), which can never be coded with M35.89 on the same claim.

Sibling codes

Other billable codes under M35.8 (laterality / anatomic variants).

M35.81

Multisystem inflammatory syndrome

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01What conditions are indexed to M35.89?

The ICD-10-CM Alphabetic Index routes eosinophilia-myalgia syndrome and 'collagen vascular disease NOS, specified NEC' directly to M35.89. Any other confirmed systemic connective tissue disorder that lacks a dedicated code also lands here.

02Can M35.89 be the principal diagnosis on an orthopedic claim?

Yes, if the systemic connective tissue disorder is the primary reason for the encounter. More commonly it appears as a secondary diagnosis alongside a surgical or joint procedure code, where it may qualify as a CC in DRG grouping.

03How does M35.89 differ from M35.9?

M35.89 is 'other specified' — the physician has named a specific disorder that has no dedicated code. M35.9 is 'unspecified' — the disorder is documented but not named or characterized. Always prefer M35.89 when documentation supports a named condition.

04Should I use M35.89 for multisystem inflammatory syndrome (MIS)?

No. MIS has its own code, M35.81. If post-COVID MIS is documented, assign M35.81 plus U09.9 per CMS FY2025 official coding guidelines. M35.89 is excluded for any condition that has a dedicated sibling code in the M35 block.

05Does M35.89 require a 7th character?

No. M35.89 is a 5-character code and is complete as written. No 7th-character extension applies to M-code musculoskeletal diagnoses.

06Which MS-DRGs does M35.89 group into?

Under MS-DRG v43.0, M35.89 groups to DRG 545 (connective tissue disorders with MCC), 546 (with CC), or 547 (without CC/MCC). Accurate concurrent CC/MCC coding is essential to capture appropriate DRG weight.

07Is reactive perforating collagenosis (L87.1) ever coded with M35.89?

No. The Excludes1 note at the M35 category level prohibits coding L87.1 on the same claim as any M35 code, including M35.89. Use L87.1 alone when that condition is documented.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M30-M36/M35-/M35.89
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M35.89
04
cms.gov
https://www.cms.gov/files/document/fy-2025-icd-10-cm-coding-guidelines.pdf
05
aapc.com
https://www.aapc.com/codes/icd-10-codes/M35

Mira AI Scribe

Mira's AI scribe captures the confirmed disorder name, its systemic scope, supporting lab or biopsy findings, and any impact on the current orthopedic encounter — preventing a drop to unspecified M35.9, an Excludes1 violation, or a CC/MCC miss that reduces DRG reimbursement.

See how Mira captures M35.89 documentation