2026 ICD-10-CM Diagnosis Code M05.9Rheumatoid arthritis with rheumatoid factor, unspecified

ICD-10-CM Codes›M00–M99›M05-M14›M05

ICD-10-CM M05.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M05.9 is a billable ICD-10-CM diagnosis code for rheumatoid arthritis with rheumatoid factor, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 545 through 547. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Rheumatoid arthritis and related disease.

This medical diagnosis code is frequently used in Orthopedics medical specialties to designate conditions such rheumatoid arthritis.

Code Identity

ICD-10-CM Code
M05.9
Billable Status
Yes — Valid for Submission
Code Describes
Rheumatoid arthritis with rheumatoid factor, unspecified
Short Description
Rheumatoid arthritis with rheumatoid factor, unspecified
Same as the full description in the CMS dataset.
Parent Code
M05
Rheumatoid arthritis with rheumatoid factor

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM05-M14Inflammatory polyarthropathies
CategoryM05Rheumatoid arthritis with rheumatoid factor
This CodeM05.9Rheumatoid arthritis with rheumatoid factor, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anti-citrullinated protein antibody detected
  • Anti-citrullinated protein antibody positive erosive rheumatoid arthritis
  • Rheumatoid arthritis in remission
  • Rheumatoid arthritis with erosion of joint
  • Rheumatoid factor and anti-citrullinated protein antibody positive erosive rheumatoid arthritis
  • Rheumatoid factor and anti-citrullinated protein antibody positive rheumatoid arthritis
  • Seropositive erosive rheumatoid arthritis
  • Seropositive rheumatoid arthritis
  • Seropositive rheumatoid arthritis in remission

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Arthritis, arthritic(acute) (chronic) (nonpyogenic) (subacute)
      • rheumatoid
        • seropositive

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS003
Rheumatoid arthritis and related disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Seropositive Rheumatoid Arthritis

    rheumatoid arthritis in which a patient's serum is positive for certain disease-related antibodies including anti-cyclic citrullinated peptides (anti-ccps), also called anti-citrullinated protein antibodies (acpas),and rheumatoid factor (rf). screening for anti-ccps is more specific than rf which can be found in other pathologic conditions. the production of these disease-associated antibodies may precede the development of clinical symptoms by several years. seropositive patients have a greater likelihood of developing extra-articular complications and a more severe course of disease.

Patient EducationClinical

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a form of arthritis that causes pain, swelling, and stiffness in your joints. RA is an autoimmune disease. Although it is most common in the wrist and fingers, this disease can cause your immune system to attack any joint tissue. The inflammation (swelling) that comes with RA can also affect other body parts.

The full article covers:

  • What is rheumatoid arthritis?
  • Who is more likely to get rheumatoid arthritis?
  • What causes rheumatoid arthritis?
  • What are the symptoms of rheumatoid arthritis?
  • How is rheumatoid arthritis diagnosed?
  • What are the treatments for rheumatoid arthritis?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M05.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
714.0 Rheumatoid arthritis
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replaced This code was replaced in the FY 2026 code set by:

  • M05.A - Abn rheu fctr & anti-citrul protein antibody w rheu arthrit
  • M05.A - Abn rheu fctr & anti-citrul protein antibody w rheu arthrit
  • M05.A - Abn rheu fctr & anti-citrul protein antibody w rheu arthrit
FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M05.9Overview

Is M05.9 (Rheumatoid arthritis with rheumatoid factor) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report rheumatoid arthritis with rheumatoid factor, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M05.9 group to?

When rheumatoid arthritis with rheumatoid factor, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 545, 546, 547, with relative weights from 0.8362 to 2.4817 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M05.9?

Under the General Equivalence Mappings, rheumatoid arthritis with rheumatoid factor, unspecified converts to ICD-9-CM 714.0 (rheumatoid arthritis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.