2026 ICD-10-CM Diagnosis Code M05.8AOther rheumatoid arthritis with rheumatoid factor of other specified site

ICD-10-CM Codes›M00–M99›M05-M14›M05

ICD-10-CM M05.8A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M05.8A is a billable ICD-10-CM diagnosis code for other rheumatoid arthritis with rheumatoid factor of other specified site. 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.

Code Identity

ICD-10-CM Code
M05.8A
Billable Status
Yes — Valid for Submission
Code Describes
Other rheumatoid arthritis with rheumatoid factor of other specified site
Short Description
Other rheu arthritis with rheumatoid factor of oth site
Parent Code
M05.8
Other 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 CodeM05.8AOther rheumatoid arthritis with rheumatoid factor of other specified site

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
          • specified NEC
            • specified site NEC

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

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.

Code History & ChangesHistory

Replacement M05.8A replaces the following previously assigned code(s):

  • M05.80 - Oth rheumatoid arthritis with rheumatoid factor of unsp site
FY 2021AddedAdded to the ICD-10-CM code setEffective October 1, 2020.
FY 2022–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M05.8AOverview

Is M05.8A (Other rheumatoid arthritis with rheumatoid factor) a billable code?

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

What MS-DRG does M05.8A group to?

When other rheumatoid arthritis with rheumatoid factor of other specified site 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.

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.