M05.09

Felty's syndrome affecting multiple joint sites simultaneously — the triad of seropositive rheumatoid arthritis, splenomegaly, and granulocytopenia documented across more than one anatomical region.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 6
Region: Multi-region

Drawn from CDCICD10DataAAPCCMS

Documentation tips

What should appear in the chart to support M05.09.

Source · Editorial brief grounded in 5 cited references ↓

The treating physician must document all three components of the Felty's triad: seropositive RA, splenomegaly, and granulocytopenia — each present in the clinical note or problem list.
Specify every joint region involved (e.g., bilateral wrists, bilateral knees, right shoulder) so the coder can determine whether site-specific M05.0x codes are appropriate before defaulting to M05.09.
Record current CBC with differential results showing neutropenia/granulocytopenia and any imaging or physical exam findings supporting splenomegaly to substantiate medical necessity for associated lab and imaging CPT codes.
Document positive RF and/or anti-CCP lab values with date of result to confirm seropositive status inherent in any M05.0x code.
Note any history of recurrent infections attributable to granulocytopenia — this supports higher-acuity E/M coding and downstream DRG assignment with MCC/CC.

Related CPT procedures

Procedure codes commonly billed with M05.09. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

20611 $104.21

Aspiration or injection of a major joint or bursa performed under real-time ultrasound guidance, with permanent image documentation.

96372 View procedure details

J0129 View procedure details

J1602 View procedure details

J1745 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M05.09 and adjacent codes.

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

Defaulting to M05.09 when only one or two sites are documented — review the note for laterality first; site-specific codes (e.g., M05.061 right knee, M05.071 right ankle) are preferred when individual sites can be identified.
Using M05.09 for generic seropositive RA with multiple joints: Felty's syndrome requires the full triad (RA + splenomegaly + granulocytopenia). Without documented splenomegaly and granulocytopenia, code the appropriate M05.7x or M05.8x multiple-site RA code instead.
Adding a separate seropositivity diagnosis code alongside M05.09 — seropositivity is inherent in all M05.x codes and must not be coded separately.
Confusing M05.09 (Felty's, multiple sites) with M05.00 (Felty's, unspecified site) — M05.00 is for documentation that confirms Felty's syndrome but does not specify any joint site at all, which is a weaker level of specificity and a higher audit risk.
Failing to code associated complications separately — recurrent bacterial infections, anemia, or drug-related adverse effects from RA biologics require additional codes beyond M05.09.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M05.09 is the billable code for Felty's syndrome when joint involvement spans multiple sites. Felty's syndrome is a rare, severe complication of seropositive rheumatoid arthritis defined by the clinical triad of RA, splenomegaly, and granulocytopenia (autoimmune neutropenia). The granulocytopenia places patients at significantly elevated infection risk, making precise diagnosis coding critical for care coordination and risk adjustment.

Use M05.09 when the treating physician has documented Felty's syndrome and the joint involvement is polyarticular — meaning it cannot be attributed to a single named site. If the affected joints can be individually identified and laterality assigned, site-specific codes under M05.0x (e.g., M05.061 for right knee, M05.012 for left shoulder) are more precise and preferred when documentation supports them. Fall back to M05.09 only when multiple distinct sites are documented but the clinical note does not permit individual site coding, or when the disease burden is explicitly described as polyarticular.

This code groups to MS-DRG 545/546/547 (Connective Tissue Disorders) under DRG v43.0. It is listed by CMS as a supporting ICD-10-CM code for biomarker medical necessity (CMS Article A56541), which is relevant when billing lab workup including RF, anti-CCP, and CBC with differential. Code M05.09 lives under parent M05.0 (Felty's syndrome) within the M05 block (Rheumatoid arthritis with rheumatoid factor), confirming seropositivity is an inherent component — do not add a separate seropositivity code.

Sibling codes

Other billable codes under M05.0 (laterality / anatomic variants).

M05.00

Felty's syndrome, unspecified site

Frequently asked questions

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

01What is Felty's syndrome and how does it differ from standard seropositive RA?

Felty's syndrome is a rare, severe complication of seropositive RA defined by the triad of RA, splenomegaly, and granulocytopenia. Standard seropositive RA (M05.7x, M05.8x, M05.9) does not include the hematologic and splenic components. M05.09 should only be used when all three elements are clinically documented.

02When should I use M05.09 versus a site-specific Felty's code like M05.061?

Use site-specific codes (M05.011–M05.079) whenever the note identifies individual joints with laterality. Reserve M05.09 for encounters where the physician documents multiple distinct joint regions affected by Felty's syndrome but does not provide enough detail to code each site separately.

03Can M05.09 be used for juvenile rheumatoid arthritis patients?

No. Juvenile rheumatoid arthritis is coded to M08.- codes. The M05.x block applies exclusively to adult-onset rheumatoid arthritis with rheumatoid factor. If the patient is a juvenile with RA-like disease plus splenomegaly and granulocytopenia, query the physician for clarification before assigning M05.09.

04Does M05.09 support medical necessity for RF and anti-CCP lab billing?

Yes. CMS Coverage Article A56541 lists M05.09 in Group 2 ICD-10-CM codes that support medical necessity for biomarker testing, including RF and anti-CCP panels. Confirm current local coverage determinations apply before submitting.

05What DRG does M05.09 map to for inpatient encounters?

M05.09 groups to MS-DRG 545 (Connective Tissue Disorders with MCC), 546 (with CC), or 547 (without CC/MCC) under DRG v43.0. Accurate documentation of complications — especially recurrent infections from granulocytopenia — can elevate the assignment to DRG 545.

06Should I code granulocytopenia or splenomegaly separately when billing M05.09?

The ICD-10-CM Tabular does not include an instructional note mandating separate coding of the triad components under M05.09, but coding the associated complications (e.g., recurrent infections, splenomegaly, neutropenia) separately is appropriate when they are actively managed and documented, as they affect DRG weight and support medical necessity.

Sources & references

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

Mira AI Scribe

Mira AI Scribe captures the Felty's triad explicitly — seropositive RA diagnosis, physical exam or imaging evidence of splenomegaly, and CBC values confirming granulocytopenia — along with every named joint region showing inflammatory involvement. This prevents downcoding to unspecified-site M05.00 or generic seropositive RA codes, and eliminates audit exposure from missing triad documentation when M05.09 is submitted with biomarker or biologic injection claims.

See how Mira captures M05.09 documentation