M05.40 Rheumatoid myopathy with rheumatoid arthritis of unspecified site

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applies from M05 Rheumatoid arthritis with rheumatoid factor

Excludes1 (never code together)

• rheumatic fever (I00)
• juvenile rheumatoid arthritis (M08.-)
• rheumatoid arthritis of spine (M45.-)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
• CMS-HCC V22: HCC 40 — Rheumatoid Arthritis and Inflammatory Connective Tissue Disease
• RxHCC V08: HCC 83 — Rheumatoid Arthritis and Other Inflammatory Polyarthropathy
• ESRD V24: HCC 40

MS-DRG index

Defines the logic of DRG(s) 545-547 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 359.6 Symptomatic inflammatory myopathy in diseases classified elsewhere (approximate)
• 714.0 Rheumatoid arthritis (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Unspecified code (laterality): Unspecified codes for which a more specific code identifying laterality (right, left, bilateral) exists within the same code family.

Code annotations containing back-references to M05.40

Back-references to M05

• Code Also: I27.21 Secondary pulmonary arterial hypertension ("rheumatoid arthritis (M05.-)")
• Type 1 Excludes: R76.81 Abnormal rheumatoid factor and anti-citrullinated protein antibody without rheumatoid arthritis ("rheumatoid arthritis with rheumatoid factor (M05.-)")

Diagnosis Index entries for M05.40

• Rheumatoid › myopathy

Nearby codes

• M05.371 Rheumatoid heart disease with rheumatoid arthritis of right ankle and foot
• M05.372 Rheumatoid heart disease with rheumatoid arthritis of left ankle and foot
• M05.379 Rheumatoid heart disease with rheumatoid arthritis of unspecified ankle and foot
• M05.39 Rheumatoid heart disease with rheumatoid arthritis of multiple sites
• M05.4 Rheumatoid myopathy with rheumatoid arthritis
• M05.40 Rheumatoid myopathy with rheumatoid arthritis of unspecified site (this code)
• M05.41 Rheumatoid myopathy with rheumatoid arthritis of shoulder
• M05.411 Rheumatoid myopathy with rheumatoid arthritis of right shoulder
• M05.412 Rheumatoid myopathy with rheumatoid arthritis of left shoulder
• M05.419 Rheumatoid myopathy with rheumatoid arthritis of unspecified shoulder
• M05.42 Rheumatoid myopathy with rheumatoid arthritis of elbow