M05.012 ICD-10-CM Code: Felty's syndrome, left shoulder
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Inflammatory polyarthropathies (M05-M14)
M05.012
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceFelty's syndrome, left shoulder
Felty's syndrome affecting the left shoulder, characterized by rheumatoid arthritis, enlarged spleen, and low white blood cell count.
Buddy Insight
Felty's syndrome affecting the left shoulder represents a severe rheumatoid arthritis variant requiring intensive monitoring due to the combination of joint destruction, immunosuppression from neutropenia, and systemic complications.
CMS-HCC V28
MappedHCC 93
RAF 0.617
CMS-HCC V24
MappedHCC 40
RAF 0.421
ACA/HHS
MappedHCC 56
Varies by metal level
ESRD/PACE
MappedHCC 40
RAF 0.058
RXHCC
MappedHCC 83
RAF 0.222
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M05.012 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M05.012 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M05.012 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M05.012 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M05.012 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M05.012 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M05.012 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is M05.012 an HCC code?
Yes. M05.012 (Felty's syndrome, left shoulder) maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under V24), with a community non-dual aged RAF of 0.617. It is billable for payment year 2026.
Coder answer: M05.012 is billable and maps to V28 HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M05.012
- Description
- Felty's syndrome, left shoulder
- HCC (V28)
- HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
- RAF
- 0.617
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.
Work M05.012 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for M05.012
For M05.012 to 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 M05.012 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
M05.012 is the ICD-10-CM diagnosis code for felty's syndrome, left shoulder. Felty's syndrome affecting the left shoulder, characterized by rheumatoid arthritis, enlarged spleen, and low white blood cell count. M05.012 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering inflammatory polyarthropathies (m05-m14).
Under the CMS-HCC V28 risk adjustment model, M05.012 maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders (HCC 93) with a community, non-dual, aged base RAF weight of 0.617. Under the older CMS-HCC V24 model, M05.012 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 40) with a community, non-dual, aged base RAF weight of 0.421. 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.
Confirm left shoulder is the documented site of involvement in the clinical record. Because M05.012 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 M05.012 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm left shoulder is the documented site of involvement in the clinical record
- •Do not use this code if only right shoulder or bilateral shoulders are affected
Clinical Significance
Felty's syndrome affecting the left shoulder represents a severe rheumatoid arthritis variant requiring intensive monitoring due to the combination of joint destruction, immunosuppression from neutropenia, and systemic complications. The condition demands multidisciplinary care including rheumatology, hematology, and infectious disease management.
Documentation Requirements
- ✓Documentation of rheumatoid arthritis affecting the left shoulder joint specifically
- ✓Evidence of splenomegaly through physical examination or imaging studies
- ✓Laboratory confirmation of neutropenia with specific white blood cell counts
- ✓Left shoulder joint involvement clearly documented
- ✓Clinical assessment of joint inflammation and range of motion limitations
- ✓History of infections or immune system complications
- ✓Current treatment regimen and response documentation
- ✓Differential diagnosis ruling out other causes of the triad
Commonly Confused Codes
- •M05.9: Seropositive rheumatoid arthritis without the Felty's syndrome triad
- •M06.00: Rheumatoid arthritis without organ or systems involvement
- •D70.4: Cyclic neutropenia without rheumatoid arthritis component
- •K63.2: Fistula of intestine, when spleen involvement is misinterpreted
- •M05.011: Same condition but affecting right shoulder instead