2026 ICD-10-CM Diagnosis Code M60.161Interstitial myositis, right lower leg

ICD-10-CM Codes›M00–M99›M60-M63›M60

ICD-10-CM M60.161
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M60.161 is a billable ICD-10-CM diagnosis code for interstitial myositis, right lower leg. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 557 through 558. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Muscle disorders.

Code Identity

ICD-10-CM Code
M60.161
Billable Status
Yes — Valid for Submission
Code Describes
Interstitial myositis, right lower leg
Short Description
Interstitial myositis, right lower leg
Same as the full description in the CMS dataset.
Parent Code
M60.16
Interstitial myositis, lower leg

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM60-M63Disorders of muscles
CategoryM60Myositis
This CodeM60.161Interstitial myositis, right lower leg

Clinical ClassificationClinical

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

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

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 M60.161 to ICD-9-CMHistory

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

ICD-9-CM
728.81 Interstitial myositis
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 M60.161Overview

Is M60.161 (Interstitial myositis, lower leg) a billable code?

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

What MS-DRG does M60.161 group to?

When interstitial myositis, right lower leg is the principal diagnosis on an inpatient stay, it groups to MS-DRG 557, 558, with relative weights from 0.8932 to 1.4869 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M60.161?

Under the General Equivalence Mappings, interstitial myositis, right lower leg converts to ICD-9-CM 728.81 (interstitial myositis). 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.