2027 ICD-10-CM Diagnosis Code D89.9Disorder involving the immune mechanism, unspecified
ICD-10-CM Codes›D50–D89›D80-D89›D89
- Billable — Valid for Submission
- Chronic Condition
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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 814 through 816. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.
D89.9 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 47 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 47, ESRD (V21) category 47, ESRD (V24) category 47, and RxHCC Part D (V08) category 99 for payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
D89.9 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Abnormal host defense
- Abnormal host response
- Abnormal immune system function
- 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
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to D89.9: its own notes plus those printed at D89, block D80-D89, and Chapter 3. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- defects in the complement system
- immunodeficiency disorders, except human immunodeficiency virus [HIV] disease
- sarcoidosis
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Immune disease NOS
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- transplant failure and rejection (T86.-)
- human immunodeficiency virus [HIV] disease (B20)
- autoimmune disease (systemic) NOS (M35.9)
- certain conditions originating in the perinatal period (P00-P96)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- human immunodeficiency virus [HIV] disease (B20)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name D89.9, its category, or a range that includes it.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
immune D89.9
Disorder (of) See Also: Disease;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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.
Code HistoryHistory
Questions About D89.9Overview
What is the ICD-10 code for disorder involving the immune mechanism, unspecified?
The ICD-10-CM code for disorder involving the immune mechanism, unspecified is D89.9 (sometimes written as D899). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
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, 2026 through September 30, 2027.
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 816, 814, 815, with relative weights from 0.7378 to 2.0727 depending on complications. Higher weights mean higher Medicare reimbursement.
Can D89.9 be reported with R77.1?
Not as a rule. The Excludes1 note at D89, which applies to D89.9, lists "hyperglobulinemia NOS (R77.1)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
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.
Does D89.9 risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage. D89.9 mapped to HCC 47 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 47 (Disorders of Immunity), ESRD (V21) category 47 (Disorders of Immunity), ESRD (V24) category 47 (Disorders of Immunity), and RxHCC Part D (V08) category 99 (Immune Disorders).
