2026 ICD-10-CM Diagnosis Code M60.80Other myositis, unspecified site

ICD-10-CM Codes›M00–M99›M60-M63›M60

ICD-10-CM M60.80
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M60.80 is a billable ICD-10-CM diagnosis code for other myositis, unspecified site. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 555 through 556. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Muscle disorders.

Code Identity

ICD-10-CM Code
M60.80
Billable Status
Yes — Valid for Submission
Code Describes
Other myositis, unspecified site
Short Description
Other myositis, unspecified site
Same as the full description in the CMS dataset.
Parent Code
M60.8
Other myositis

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM60-M63Disorders of muscles
CategoryM60Myositis
This CodeM60.80Other myositis, unspecified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Adult-onset overlap myositis
  • Autoimmune inflammation of skeletal muscle
  • Benign acute myositis
  • Eosinophilic myopathy
  • Eosinophilic myositis
  • Focal nodular myositis
  • Idiopathic eosinophilia
  • Idiopathic eosinophilic myositis
  • Idiopathic inflammatory myopathy
  • Infection caused by Toxocara
  • Juvenile overlap myositis
  • Macrophagic myofasciitis
  • Muscle eosinophilia
  • Nematode myositis
  • Paraneoplastic myositis
  • Parasitic myositis
  • Proliferative myositis
  • Reactive fibrous tissue proliferation
  • Toxocariasis myositis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Myositis
      • specified type NEC

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS026
Muscle disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Proliferative Myositis

    a rapidly growing, poorly circumscribed, mass-forming proliferation that arises from the skeletal muscle. it is characterized by the presence of spindle-shaped fibroblasts, round ganglion-like cells, myxoid to collagenous stroma formation, and high mitotic activity. it recurs only rarely following local excision and does not metastasize.

Patient EducationClinical

Myositis

Myositis means inflammation of the muscles that you use to move your body. An injury, infection, or autoimmune disease can cause it. Two specific kinds are polymyositis and dermatomyositis. Polymyositis causes muscle weakness, usually in the muscles closest to the trunk of your body.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M60.80 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
729.1 Myalgia and myositis NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M60.80Overview

Is M60.80 (Other myositis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other myositis, unspecified site on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M60.80 group to?

When other myositis, unspecified site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 555, 556, with relative weights from 0.8306 to 1.3218 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M60.80?

Under the General Equivalence Mappings, other myositis, unspecified site converts to ICD-9-CM 729.1 (myalgia and myositis NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.