M05.779: Rheumatoid arthritis with rheumatoid factor of unspecified ankle and foot without organ or systems involvement

M05.779, rheumatoid arthritis with rheumatoid factor of unspecified ankle and foot without organ or systems involvement, is listed as a covered diagnosis in 3 Medicare billing and coding articles that apply to 8 HCPCS Level II codes, including J1745 (Injection, infliximab, excludes biosimilar, 10 mg), Q5104 (Injection, infliximab-abda, biosimilar, (renflexis), 10 mg), Q5103 (Injection, infliximab-dyyb, biosimilar, (inflectra), 10 mg). The articles come from 2 Medicare contractors. A listed diagnosis supports medical necessity only; coverage still depends on the LCD's criteria and on documentation in the medical record.

HCPCS Level II codes with M05.779 as a covered diagnosis

CodeDescriptionMedicare coverageDMEPOS fee 2026 (state range)Articles listing it
J1745Injection, infliximab, excludes biosimilar, 10 mgSpecial coverage instructions apply—2
Q5104Injection, infliximab-abda, biosimilar, (renflexis), 10 mgSpecial coverage instructions apply—2
Q5103Injection, infliximab-dyyb, biosimilar, (inflectra), 10 mgSpecial coverage instructions apply—2
Q5121Injection, infliximab-axxq, biosimilar, (avsola), 10 mgCarrier judgment—2
J9312Injection, rituximab, 10 mgSpecial coverage instructions apply—1
Q5123Injection, rituximab-arrx, biosimilar, (riabni), 10 mgCarrier judgment—1
Q5119Injection, rituximab-pvvr, biosimilar, (ruxience), 10 mgCarrier judgment—1
Q5115Injection, rituximab-abbs, biosimilar, (truxima), 10 mgSpecial coverage instructions apply—1

Medicare policy articles listing M05.779

A diagnosis listed as covered in a billing and coding article supports medical necessity for the article's codes; it does not guarantee payment. Coverage depends on the LCD's criteria, the contractor's jurisdiction and documentation in the medical record.

Other M05 diagnoses (Rheumatoid arthritis with rheumatoid factor)

Frequently asked questions

Does Medicare cover M05.779 (Rheumatoid arthritis with rheumatoid factor of unspecified…)?

Medicare covers items and services, not diagnoses. 3 Medicare billing and coding articles list M05.779 as a covered diagnosis for 8 HCPCS Level II codes: the diagnosis can support medical necessity for those codes, but payment still depends on the LCD's coverage criteria and the medical record.

Which HCPCS codes can be billed with ICD-10 M05.779?

The Level II codes from the policies most specific to this diagnosis are J1745 (Injection, infliximab, excludes biosimilar, 10 mg, 2 articles); Q5104 (Injection, infliximab-abda, biosimilar, (renflexis), 10 mg, 2 articles); Q5103 (Injection, infliximab-dyyb, biosimilar, (inflectra), 10 mg, 2 articles); Q5121 (Injection, infliximab-axxq, biosimilar, (avsola), 10 mg, 2 articles); J9312 (Injection, rituximab, 10 mg, 1 article). Code choice depends on the item supplied; check each code's descriptor.

Which Medicare policy articles list M05.779?

A56432 (Billing and Coding: Infliximab); A52423 (Billing and Coding: Infliximab and biosimilars); A59101 (Billing and Coding: Off-label Use of Rituximab and Rituximab Biosimilars).

What is ICD-10-CM code M05.779?

M05.779 is the ICD-10-CM code for rheumatoid arthritis with rheumatoid factor of unspecified ankle and foot without organ or systems involvement, in category M05 (Rheumatoid arthritis with rheumatoid factor), chapter 13: Diseases of the musculoskeletal system and connective tissue.

Next steps

Sources: CMS Medicare Coverage Database billing and coding articles (covered ICD-10 code lists and HCPCS links); ICD-10-CM FY2026; CMS HCPCS Level II release October 2026; CMS DMEPOS fee schedule 2026 (non-rural state fees). Not billing or legal advice.

Chapter 13: Diseases of the musculoskeletal system and connective tissue · All diagnoses · HCPCS lookup