2026 ICD-10-CM Diagnosis Code M05.121Rheumatoid lung disease with rheumatoid arthritis of right elbow

ICD-10-CM Codes›M00–M99›M05-M14›M05

ICD-10-CM M05.121
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M05.121 is a billable ICD-10-CM diagnosis code for rheumatoid lung disease with rheumatoid arthritis of right elbow. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 196 through 198. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified lower respiratory disease and Rheumatoid arthritis and related disease.

Code Identity

ICD-10-CM Code
M05.121
Billable Status
Yes — Valid for Submission
Code Describes
Rheumatoid lung disease with rheumatoid arthritis of right elbow
Short Description
Rheumatoid lung disease w rheumatoid arthritis of r elbow
Parent Code
M05.12
Rheumatoid lung disease with rheumatoid arthritis of elbow

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM05-M14Inflammatory polyarthropathies
CategoryM05Rheumatoid arthritis with rheumatoid factor
This CodeM05.121Rheumatoid lung disease with rheumatoid arthritis of right elbow

Clinical ClassificationClinical

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

CCSR RSP016
Other specified and unspecified lower respiratory disease
Default principal diagnosis: inpatient No · outpatient No
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.

Convert M05.121 to ICD-9-CMHistory

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

ICD-9-CM
714.81 Rheumatoid lung
Approximate The match is approximate rather than exact.

Code HistoryHistory

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 M05.121Overview

Is M05.121 (Rheumatoid lung disease with rheumatoid arthritis of elbow) a billable code?

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

What MS-DRG does M05.121 group to?

When rheumatoid lung disease with rheumatoid arthritis of right elbow is the principal diagnosis on an inpatient stay, it groups to MS-DRG 196, 197, 198, with relative weights from 0.7162 to 1.8872 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M05.121?

Under the General Equivalence Mappings, rheumatoid lung disease with rheumatoid arthritis of right elbow converts to ICD-9-CM 714.81 (rheumatoid lung). 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.