M35.5
BillableMultifocal fibrosclerosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M35.5 an HCC code?
Yes. M35.5 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under the V24 model but is not retained in V28.
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for M35.5
For M35.5to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M35.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M35.5 is the ICD-10-CM diagnosis code for multifocal fibrosclerosis. Multifocal fibrosclerosis is a rare condition characterized by fibrosis (scarring) occurring in multiple locations throughout the body, such as the lungs, heart, or abdomen. M35.5 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering systemic connective tissue disorders (m30-m36).
Under the older CMS-HCC V24 model, M35.5 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 40) with a community, non-dual, aged base RAF weight of 0.307. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Document the specific anatomical sites affected by fibrosis for complete clinical documentation. Because M35.5 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M35.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the specific anatomical sites affected by fibrosis for complete clinical documentation
- •This is a rare diagnosis; ensure thorough documentation and imaging confirmation are present
Clinical Significance
Multifocal fibrosclerosis represents a rare and serious condition causing progressive fibrosis in multiple organs, requiring specialized monitoring and management to prevent organ failure. The multi-organ involvement necessitates coordinated subspecialty care and frequent surveillance for disease progression.
Documentation Requirements
- ✓Documentation of fibrotic involvement in multiple anatomic sites
- ✓Histopathologic evidence of fibrosis from affected organs
- ✓Imaging studies demonstrating multi-organ fibrotic changes
- ✓Exclusion of other causes of systemic fibrosis
- ✓Assessment of organ function in affected systems
- ✓Documentation of disease progression or stability
- ✓Treatment response to anti-fibrotic or immunosuppressive therapies
Commonly Confused Codes
- •M34.9 — Systemic sclerosis, unspecified (different fibrotic condition)
- •K74.60 — Unspecified cirrhosis of liver (single organ fibrosis)
- •J84.10 — Pulmonary fibrosis, unspecified (single organ involvement)
- •N26.9 — Renal sclerosis, unspecified (single organ involvement)
- •M35.9 — Systemic involvement of connective tissue, unspecified (less specific)