M05.779 — Rheumatoid arthritis with rheumatoid factor of unspecified ankle and foot without organ or systems involvement
Is M05.779 billable?
Yes, but M05.779 is an unspecified code. M05.779 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, M05.779 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting M05.779 — the more specific alternatives are listed below.
M05.779 at a glance
| Code | M05.779 |
|---|---|
| Description | Rheumatoid arthritis with rheumatoid factor of unspecified ankle and foot without organ or systems involvement |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does M05.779 group to?
M05.779 sits in MDC 08 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 545Connective Tissue Disorders with MCCmedical
- 546Connective Tissue Disorders with CCmedical
- 547Connective Tissue Disorders without CC/MCCmedical
How is M05.779 listed in the Alphabetic Index?
The Alphabetic Index lists these routes under M05.77, the nearest indexed parent of M05.779. Use them to find the family, then select the specific code.
- Arthritis, arthritic › rheumatoid › seropositive › without organ involvement › ankle (acute) (chronic) (nonpyogenic) (subacute)
- Arthritis, arthritic › rheumatoid › seropositive › without organ involvement › foot joint (acute) (chronic) (nonpyogenic) (subacute)
Excludes1 — never code together — inherited from M05
The conditions below can never be reported together with M05.779 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes2 — not included here — inherited from Chapter 13
The conditions below are not part of M05.779, but a patient may have both at the same time. When documentation supports it, M05.779 and the excluded code may both be reported.
- arthropathic psoriasis (L40.5-)
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- compartment syndrome (traumatic) (T79.A-)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
How long has M05.779 existed?
M05.779 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.