2026 ICD-10-CM Diagnosis Code B26.85Mumps arthritis

ICD-10-CM Codes›A00–B99›B25-B34›B26

ICD-10-CM B26.85
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B26.85 is a billable ICD-10-CM diagnosis code for mumps arthritis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 865 through 866. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Infective arthritis and Viral infection.

Code Identity

ICD-10-CM Code
B26.85
Billable Status
Yes — Valid for Submission
Code Describes
Mumps arthritis
Short Description
Mumps arthritis
Same as the full description in the CMS dataset.
Parent Code
B26.8
Mumps with other complications

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB25-B34Other viral diseases
CategoryB26Mumps
This CodeB26.85Mumps arthritis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Mumps arthritis

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.

    • Arthritis, arthritic(acute) (chronic) (nonpyogenic) (subacute)
      • in (due to)
        • mumps
    • Mumps
      • arthritis

Clinical ClassificationClinical

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

CCSR MUS001
Infective arthritis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Mumps

Mumps is an illness caused by the mumps virus. It starts with:

Read the full article at MedlinePlus

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

Convert B26.85 to ICD-9-CMHistory

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

ICD-9-CM
072.79 Mumps complication NEC
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 B26.85Overview

Is B26.85 (Mumps with other complications) a billable code?

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

What MS-DRG does B26.85 group to?

When mumps arthritis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 865, 866, with relative weights from 0.8696 to 1.4983 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of B26.85?

Under the General Equivalence Mappings, mumps arthritis converts to ICD-9-CM 072.79 (mumps complication NEC). 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.