M05.00

Felty's syndrome coded at the unspecified-site level — rheumatoid arthritis with positive rheumatoid factor, splenomegaly, and granulocytopenia/neutropenia, where the affected joint site is not documented.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 5
Region: Multi-region

Drawn from CDCICD10DataAAPCRheumatologyadvisorCMS

Documentation tips

What should appear in the chart to support M05.00.

Source · Editorial brief grounded in 5 cited references ↓

Document all three components of the Felty's triad explicitly: seropositive RA, splenomegaly, and neutropenia/granulocytopenia — payers and auditors look for clinical support of this specific syndrome designation.
If a specific joint site is involved and documented, code to that site (M05.01–M05.09) rather than defaulting to M05.00 unspecified; query the provider if the note mentions joint involvement without naming the site.
Record the results of CBC with differential to substantiate the leukopenia/neutropenia component — lab findings in the record anchor the Felty's diagnosis against audit challenge.
Document positive rheumatoid factor lab results (RF titer or anti-CCP) to satisfy the seropositive RA requirement that distinguishes M05 codes from seronegative RA (M06.-).
Note splenomegaly findings — physical exam or imaging — to support the splenoadenomegaly criterion; a provider assertion alone without clinical correlates is an audit vulnerability.

Related CPT procedures

Procedure codes commonly billed with M05.00. 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.

20610 $68.81

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

96372 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M05.00 and adjacent codes.

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

Defaulting to M05.00 when the note actually documents a specific joint site — review the full encounter note before accepting the unspecified code; site-specific codes (M05.01–M05.09) are required when laterality and joint are documented.
Confusing M05.00 with seronegative RA codes (M06.-) — Felty's syndrome requires documented positive rheumatoid factor; if seropositivity is not confirmed, M05.0x is not supportable.
Coding only the Felty's syndrome code and omitting separately reportable comorbidities such as neutropenia (D70.-) or splenomegaly when those conditions are managed as distinct problems during the encounter.
Using parent code M05.0, which is non-billable — M05.00 (or a site-specific child code) is required on all claims.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M05.00 is the billable code for Felty's syndrome when no specific joint site is documented in the record. Felty's syndrome is a severe, rare complication of seropositive rheumatoid arthritis defined by the triad of RA with rheumatoid factor, splenomegaly (splenoadenomegaly), and leukopenia (primarily granulocytopenia/neutropenia). The neutropenia drives elevated infection risk and is the primary driver of morbidity beyond the underlying RA.

Use M05.00 only when the treating provider has not documented a specific joint site involved. If the clinician documents a specific joint — shoulder, elbow, wrist, hand, hip, knee, or ankle/foot — a more specific code in the M05.01–M05.09 range is required and will support higher specificity on the claim. For bilateral or multiple-joint involvement, M05.09 (multiple sites) applies. M05.00 is appropriate as a fallback when site documentation is genuinely absent, not as a shortcut when the note contains laterality and joint information.

Felty's syndrome sits within the M05 block (Rheumatoid arthritis with rheumatoid factor). It is excluded from juvenile RA (M08.-) and rheumatoid arthritis of the spine (M45.-). MS-DRG v43.0 groups M05.00 into DRGs 545–547 (Connective tissue disorders with/without MCC/CC), making accurate documentation of comorbidities and complications material to reimbursement.

Sibling codes

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

M05.09

Felty's syndrome, multiple sites

Frequently asked questions

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

01When is M05.00 the correct code versus a site-specific M05.0x code?

Use M05.00 only when the provider's documentation does not identify a specific joint site. If the note names shoulder, elbow, wrist, hand, hip, knee, or ankle/foot, the corresponding site-specific code (M05.011–M05.079) is required. If multiple joints are involved, use M05.09.

02Is M05.0 billable on a claim?

No. M05.0 is a non-billable parent code. M05.00 is the minimum billable level for unspecified site; site-specific codes (M05.011, M05.012, etc.) are billable for documented joint locations.

03Does Felty's syndrome require a positive rheumatoid factor to code M05.00?

Yes. The entire M05 block is restricted to rheumatoid arthritis with rheumatoid factor (seropositive RA). If seropositivity is not documented, you cannot use M05.0x — consider M06.- for seronegative presentations.

04Should neutropenia be coded separately when Felty's syndrome is coded?

Code separately only if the neutropenia is being independently evaluated, managed, or is clinically significant to the encounter beyond the Felty's diagnosis itself. Follow standard ICD-10-CM multiple coding guidance; do not routinely add D70.- unless it drives additional workup or treatment at that visit.

05Which MS-DRGs does M05.00 map to?

Under MS-DRG v43.0, M05.00 groups to DRG 545 (Connective tissue disorders with MCC), DRG 546 (with CC), or DRG 547 (without CC/MCC), depending on documented comorbidities and complications.

06Can M05.00 be used for juvenile patients with Felty's syndrome features?

No. Juvenile rheumatoid arthritis is excluded from M05 by a Type 1 Excludes note — use the appropriate M08.- code for patients with juvenile-onset disease.

07Does Felty's syndrome involving the spine code to M05.00?

No. Rheumatoid arthritis of the spine is excluded from M05 by a Type 1 Excludes note. Spinal involvement maps to M45.- (ankylosing spondylitis) or the appropriate spondylopathy code, not M05.0x.

Sources & references

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

01CDC ICD-10-CM Tabular List 2026 — M05.00
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M05-M14/M05-/M05.00
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M05.00
04
rheumatologyadvisor.com
https://www.rheumatologyadvisor.com/diagnostic-update/rheumatology-icd-10-codes/
05CMS MS-DRG v43.0 Grouper — DRGs 545–547

Mira AI Scribe

Mira's AI scribe captures the Felty's triad from the encounter note — documented positive rheumatoid factor, spleen size or splenomegaly notation, and CBC differential showing neutropenia/granulocytopenia — plus any specific joint sites mentioned by the provider. Capturing joint site prevents the claim from landing on M05.00 when a more specific M05.01–M05.09 code is warranted, avoiding a specificity downcode and potential audit flag.

See how Mira captures M05.00 documentation