M05.40 — Rheumatoid myopathy with rheumatoid arthritis of unspecified site

BillableUnspecifiedCC

Is M05.40 billable?

Yes, but M05.40 will trip a Medicare edit. M05.40 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, CMS lists M05.40 under Medicare Code Editor edit 20, “Unspecified code” — meaning a code specifying laterality (right, left or bilateral) exists in the same family. On an inpatient claim this triggers the edit, because CMS holds that there are very limited circumstances in which laterality cannot be documented.

More specific alternatives

M05.40 at a glance

Code	M05.40
Description	Rheumatoid myopathy with rheumatoid arthritis of unspecified site
Billable	Yes
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027

What Medicare edits apply to M05.40?

The Medicare Code Editor screens inpatient claims before they are grouped. These edits name M05.40 directly.

Unspecified — a laterality-specific code exists — MCE edit 20

A code specifying laterality (right, left or bilateral) exists in the same family. CMS holds that there are very limited circumstances in which laterality cannot be documented.

Which MS-DRGs does M05.40 group to?

M05.40 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

As a secondary diagnosis, M05.40 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.

How is M05.40 listed in the Alphabetic Index?

These are the routes through the Alphabetic Index that lead to M05.40. They show the wording a clinician may have documented, which often differs from the Tabular description.

Rheumatoid › myopathy

Excludes1 — never code together — inherited from M05

The conditions below can never be reported together with M05.40 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.

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

Excludes2 — not included here — inherited from Chapter 13

The conditions below are not part of M05.40, but a patient may have both at the same time. When documentation supports it, M05.40 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 M05.40 existed?

M05.40 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.