2026 ICD-10-CM Diagnosis Code D89.9Disorder involving the immune mechanism, unspecified

ICD-10-CM Codes›D50–D89›D80-D89›D89

ICD-10-CM D89.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D89.9 is a billable ICD-10-CM diagnosis code for disorder involving the immune mechanism, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 814 through 816. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.

Code Identity

ICD-10-CM Code
D89.9
Billable Status
Yes — Valid for Submission
Code Describes
Disorder involving the immune mechanism, unspecified
Short Description
Disorder involving the immune mechanism, unspecified
Same as the full description in the CMS dataset.
Parent Code
D89
Other disorders involving the immune mechanism, not elsewhere classified

Code Classification

ChapterD50–D89Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
SectionD80-D89Certain disorders involving the immune mechanism
CategoryD89Other disorders involving the immune mechanism, not elsewhere classified
This CodeD89.9Disorder involving the immune mechanism, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abnormal host defense
  • Abnormal host response
  • Acquired ataxia
  • Acute nephritis due to another disorder
  • Acute tubulointerstitial nephritis
  • Acute tubulo-interstitial nephritis due to immunological disorder
  • Antibody-mediated activation and inactivation
  • Ataxia due to disorder of immune function
  • Autoimmune AND/OR graft reaction
  • Autoimmune reaction
  • Autoimmune state
  • Autoimmune vasculitis
  • Autonomic neuropathy due to disorder of immune function
  • Chorea due to immunological disorder
  • Chronic disease of immune function
  • Chronic disease of immune structure
  • Cryopathy
  • Disorder of immune function
  • Disorder of immune function due to systemic lupus erythematosus
  • Disorder of immune structure
  • Drug-induced autoimmune reaction
  • Epilepsy due to immune disorder
  • Glomerular disorders in blood diseases and disorders involving the immune mechanism
  • Granulocyte abnormality due to immune defect
  • Hereditary disorder of immune system
  • Hypertrophic pachymeningitis due to disorder of immune function
  • Immune defect
  • Immune system complication of procedure
  • Immune-mediated neuropathy
  • Immunosuppression-related infectious disease
  • Induced autoimmune reaction
  • Microcephaly, hypogammaglobulinemia, abnormal immunity syndrome
  • Nonspecific immune reaction
  • Pachymeningitis
  • Panniculitis due to immunological disorder
  • Postvaccinal autoimmune reaction
  • Spondyloenchondrodysplasia
  • Spondyloenchondrodysplasia with immune dysregulation
  • Ulcer of esophagus due to disorder of immune system

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Immune disease NOS

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.

    • Disease, diseased
      • immune
    • Disorder(of)
      • immune mechanism (immunity)

Clinical ClassificationClinical

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

CCSR BLD008
Immunity disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Immune System and Disorders

Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.

The full article covers:

  • What is the immune system?
  • What are the parts of the immune system?
  • How does the immune system work?
  • What are the types of immunity?
  • What can go wrong with the immune system?

Read the full article at MedlinePlus

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

Convert D89.9 to ICD-9-CMHistory

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

ICD-9-CM
279.9 Immune mechanism dis NOS
Exact Match The mapping is direct, with no qualifiers.

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 D89.9Overview

Is D89.9 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report disorder involving the immune mechanism, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does D89.9 group to?

When disorder involving the immune mechanism, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 814, 815, 816, with relative weights from 0.6320 to 2.1267 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of D89.9?

Under the General Equivalence Mappings, disorder involving the immune mechanism, unspecified converts to ICD-9-CM 279.9 (immune mechanism dis NOS). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.