2026 ICD-10-CM Diagnosis Code D89.84IgG4-related disease

ICD-10-CM Codes›D50–D89›D80-D89›D89

ICD-10-CM D89.84
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D89.84 is a billable ICD-10-CM diagnosis code for IgG4-related disease. 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.

For Medicare Advantage risk adjustment, D89.84 maps to CMS-HCC Category 115 (Specified Immunodeficiencies and White Blood Cell Disorders) under the V28 model, adding a risk factor of about 0.565 for a community, non-dual, aged beneficiary in payment year 2026.

Code Identity

ICD-10-CM Code
D89.84
Billable Status
Yes — Valid for Submission
Code Describes
IgG4-related disease
Short Description
IgG4-related disease
Same as the full description in the CMS dataset.
Parent Code
D89.8
Other specified 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 CodeD89.84IgG4-related disease

Medicare Risk Adjustment (HCC)Billing

D89.84 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.

CMS-HCC V28 Category (Payment Model)
HCC 115— Specified Immunodeficiencies and White Blood Cell Disorders
Payment HCC · PY 2026 one of 19 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.565
community, non-dual, aged · ranges 0.302–0.692 across segments
Hierarchy
Superseded by HCC 114
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 47
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 47 · ESRD (V21): HCC 47 · ESRD (V24): HCC 47
ESRD V21 weights: 0.097 dialysis, 0.549–0.688 functioning graft · ESRD V24 weights: 0.078 dialysis, 0.523–0.803 functioning graft
Part D (RxHCC)
RxHCC 99 — Immune Disorders
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 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.

  • Autoimmune cholangitis
  • Autoimmune hypophysitis
  • Autoimmune thyroiditis
  • IgG4-related sclerosing cholangitis
  • Immunoglobulin G4 related aortitis
  • Immunoglobulin G4 related disease
  • Immunoglobulin G4 related eosinophilic angiocentric fibrosis
  • Immunoglobulin G4 related hypophysitis
  • Immunoglobulin G4 related kidney disease
  • Immunoglobulin G4 related ophthalmic disease
  • Immunoglobulin G4 related pachymeningitis
  • Immunoglobulin G4 related periaortitis
  • Immunoglobulin G4 related submandibular gland disease
  • Immunoglobulin G4 related thyroid disease
  • Pachymeningitis
  • Sclerosing cholangitis
  • Secondary sclerosing cholangitis
  • Sialoadenitis of the submandibular gland

Tabular List NotesGuidance

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

Inclusion Terms

  • Immunoglobulin G4-related disease

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

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

Clinical InformationClinical

  • Autoimmune Hypophysitis

    immune-mediated inflammation of the pituitary gland often associated with other autoimmune diseases (e.g., hashimoto disease; graves disease; and addison disease).

  • Autoimmune Hypophysitis|Lymphocytic Hypophysitis

    an autoimmune condition affecting the pituitary gland, characterized by lymphocytic infiltration, commonly presenting with pituitary hormone deficiencies.

  • Grade 1 Hypophysitis, CTCAE|Grade 1 Hypophysitis

    asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated

  • Grade 2 Hypophysitis, CTCAE|Grade 2 Hypophysitis

    moderate; minimal, local or noninvasive intervention indicated; limiting age-appropriate instrumental adl

  • Grade 3 Hypophysitis, CTCAE|Grade 3 Hypophysitis

    severe or medically significant but not immediately life-threatening; hospitalization or prolongation of existing hospitalization indicated; limiting self care adl

  • Grade 4 Hypophysitis, CTCAE|Grade 4 Hypophysitis

    life-threatening consequences; urgent intervention indicated

  • Grade 5 Hypophysitis, CTCAE|Grade 5 Hypophysitis

    death

  • Hypophysitis

    an inflammatory process in the pituitary gland.

  • Hypophysitis, CTCAE|Hypophysitis

    a disorder characterized by inflammation and cellular infiltration of the pituitary gland.

  • Lymphocytic Neurohypophysitis

    an autoimmune condition affecting the posterior pituitary gland, which is characterized by lymphocytic infiltration, and which often presents as diabetes insipidus.

Code History & ChangesHistory

Replacement D89.84 replaces the following previously assigned code(s):

  • D89.89 - Oth disrd involving the immune mechanism, NEC
FY 2024AddedAdded to the ICD-10-CM code setEffective October 1, 2023.
FY 2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About D89.84Overview

What is the ICD-10 code for IgG4-related disease?

The ICD-10-CM code for IgG4-related disease is D89.84 (sometimes written as D8984). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is D89.84 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report IgG4-related disease on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does D89.84 group to?

When IgG4-related disease 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 HCC is D89.84?

D89.84 (IgG4-related disease) maps to CMS-HCC Category 115 (Specified Immunodeficiencies and White Blood Cell Disorders), commonly written as HCC 115, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 47 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 99.

Does D89.84 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, D89.84 adds a risk adjustment factor of about 0.565 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.302 to 0.692 depending on the payment segment). A more severe related category (HCC 114) supersedes it when both are reported. See the full factor table on the HCC 115 category page.