ICD-10 M35.9
Billable / Specific HCC v28: 40Systemic involvement of connective tissue, unspecified
About ICD-10-CM M35.9
ICD-10-CM code M35.9 represents Systemic involvement of connective tissue, unspecified. This is a billable/specific code in the Musculoskeletal and Connective Tissue chapter (block M35). The 2026 edition of ICD-10-CM M35.9 became effective on October 1, 2025.
Coding Tips for M35.9
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
M35.9 is a CMS-HCC v28 risk-adjustment code (category 40). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under M35.9. Per CMS ICD-10-CM Tabular 2026.
- Autoimmune disease (systemic) NOS
- Collagen (vascular) disease NOS
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for M35.9
Local Coverage Determinations (LCDs) from CMS MACs that list M35.9 as a covered diagnosis.
Showing top 10 of 30 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing M35.9.
1 Cigna
3 Medicare
2 Aetna
CPT Codes Commonly Billed with M35.9
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 11104 Punch biopsy skin — uncertain skin neoplasm, skin cancer, melanoma, nevi, psoriasis, lupus, connective tissue disorder, pemphigus, bullous pemphigoid Dermatology
Convert M35.9 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| M35.9 | 7109 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To M35.9
Other codes in section M30-M36 (Systemic connective tissue disorders).
ICD-10 M35.9, Billing FAQ
Is ICD-10 code M35.9 billable? +
Yes, M35.9 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to M35.9? +
ICD-10 M35.9 includes: Autoimmune disease (systemic) NOS; Collagen (vascular) disease NOS.
Does M35.9 affect Medicare Advantage HCC risk adjustment? +
Yes. M35.9 maps to CMS-HCC v28 category 40. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with M35.9? +
Procedures frequently paired with M35.9 include: 11104.
What ICD-9 codes does M35.9 map to? +
Per CMS GEMs, M35.9 maps to ICD-9 codes: 7109. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on July 17, 2026.
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