M01.X79 — Direct infection of unspecified ankle and foot in infectious and parasitic diseases classified elsewhere
Is M01.X79 billable?
Yes, but M01.X79 will trip a Medicare edit. M01.X79 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, CMS lists M01.X79 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.
M01.X79 at a glance
| Code | M01.X79 |
|---|---|
| Description | Direct infection of unspecified ankle and foot in infectious and parasitic diseases classified elsewhere |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
What Medicare edits apply to M01.X79?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name M01.X79 directly.
This code describes a manifestation of an underlying disease. The underlying condition must be sequenced before it, so it can never be the principal or first-listed diagnosis.
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 M01.X79 group to?
M01.X79 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.
- 548Septic Arthritis with MCCmedical
- 549Septic Arthritis with CCmedical
- 550Septic Arthritis without CC/MCCmedical
As a secondary diagnosis, M01.X79 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
Excludes1 — never code together — inherited from M01
The conditions below can never be reported together with M01.X79 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- arthropathy in Lyme disease (A69.23)
- gonococcal arthritis (A54.42)
- meningococcal arthritis (A39.83)
- mumps arthritis (B26.85)
- postinfective arthropathy (M02.-)
- postmeningococcal arthritis (A39.84)
- reactive arthritis (M02.3)
- rubella arthritis (B06.82)
- sarcoidosis arthritis (D86.86)
- typhoid fever arthritis (A01.04)
- tuberculosis arthritis (A18.01-A18.02)
Code first — inherited from M01
The underlying condition below must be sequenced before M01.X79. M01.X79 describes a manifestation and cannot be the principal or first-listed diagnosis.
Excludes2 — not included here — inherited from Chapter 13
The conditions below are not part of M01.X79, but a patient may have both at the same time. When documentation supports it, M01.X79 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 M01.X79 existed?
M01.X79 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.