Interstitial myositis involving two or more anatomical muscle sites, classified under non-infective inflammatory muscle disorders in Chapter 13.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 10
- Region
- Multi-region
Documentation tips
What should appear in the chart to support M60.19.
Source · Editorial brief grounded in 5 cited references ↓
- Specify each affected muscle site by name and laterality — if two or more distinct sites are named, code them individually using site-specific M60.1x codes rather than defaulting to M60.19.
- Document whether the myositis is classified as interstitial (connective tissue/fibrosing) versus infective, inflammatory (polymyositis), or inclusion body — each maps to a different code family.
- Record supporting diagnostic findings: CK/aldolase lab values, MRI muscle edema patterns, EMG results, and biopsy findings if performed.
- Note the absence of features pointing to inclusion body myositis (rimmed vacuoles on biopsy, selective finger flexor/quadriceps weakness) to justify use of M60.19 over G72.41.
- If myositis is a sequela of an inflammatory connective tissue disease, evaluate whether an additional code from M30-M36 is needed to capture the underlying condition.
Related CPT procedures
Procedure codes commonly billed with M60.19. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M60.19 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Defaulting to M60.19 when specific sites are documented: if the provider identifies each affected location, assign individual site-level codes from M60.11–M60.18 rather than the multi-site catch-all.
- Confusing interstitial myositis (M60.19) with inclusion body myositis (G72.41) — the Excludes2 note under M60 means they can coexist but are never equivalent; G72.41 requires biopsy-confirmed rimmed vacuoles.
- Using M60.19 for polymyositis: polymyositis codes to M33.2x, not M60.1x, and has distinct documentation and clinical validation requirements.
- Assigning M60.19 for acute traumatic muscle inflammation — acute muscle injuries are Chapter 19 (S-codes); chronic or recurrent non-infective muscle inflammation belongs in Chapter 13.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
M60.19 applies when interstitial myositis — a non-infective, fibrosing inflammatory process of muscle connective tissue — is documented at multiple sites simultaneously. Per FY2026 ICD-10-CM coding guidelines, 'multiple sites' requires involvement of two or more distinct anatomical locations. Use M60.19 only when the specific sites are not individually documented; if the provider names each affected site (e.g., right upper arm and left thigh), assign the individual site-specific codes from the M60.1x subcategory instead.
Interstitial myositis differs from inflammatory myopathies like polymyositis (M33.2x) and must not be confused with inclusion body myositis (G72.41), which carries an Excludes2 note under M60. That Excludes2 means G72.41 may be reported alongside M60 codes when both conditions are genuinely present, but they are not interchangeable — inclusion body myositis requires biopsy confirmation of rimmed vacuoles.
This code maps to MS-DRG 557 (Tendonitis, myositis and bursitis with MCC) or 558 (without MCC) under MS-DRG v42.0. In an orthopedic coding context, M60.19 most commonly appears as a secondary or differential diagnosis code. Surgical intervention is rarely the primary driver; more typical encounters involve evaluation, imaging, or biopsy to establish or refine the diagnosis.
Sibling codes
Other billable codes under M60.1 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01When should I use M60.19 instead of individual site-specific M60.1x codes?
02Is M60.19 appropriate for inclusion body myositis affecting multiple muscles?
03How does M60.19 differ from polymyositis (M33.2x)?
04Can M60.19 be used as a principal diagnosis in an orthopedic inpatient encounter?
05What imaging or lab documentation supports M60.19 at audit?
06Does M60.19 require a 7th character?
07How does the FY2026 guideline define 'multiple sites' for M60.19?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
Mira AI Scribe
The Mira AI Scribe captures documented muscle site names, laterality, lab values (CK, aldolase), MRI or EMG findings, and biopsy results from the encounter note. This specificity allows the coder to determine whether individual site-level M60.1x codes apply or whether M60.19 is warranted — preventing a multi-site default that could trigger a specificity-related claim denial or audit flag.
See how Mira captures M60.19 documentation