What is ICD-10 code D81.89?

D81.89 is the ICD-10-CM diagnosis code for Other combined immunodeficiencies. A rare condition where the immune system is weakened due to multiple genetic defects, but the specific defects do not fit into other defined categories. D81.89 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. D81.89 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. D81.89 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. D81.89 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does D81.89 map to under V28?

D81.89 maps to CMS-HCC V28 HCC 114 (Common Variable and Combined Immunodeficiencies). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM D81.89: Other combined

D81.89 maps to CMS-HCC V28 114. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · free HCC coding tools

ICD-10-CM Code View

HCC Buddy Code Card

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Code lookupD81.89Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) / Certain disorders involving the immune mechanism (D80-D89)

D81.89

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Other combined immunodeficiencies

A rare condition where the immune system is weakened due to multiple genetic defects, but the specific defects do not fit into other defined categories.

Buddy Insight

CMS-HCC V28

Mapped

HCC 114

Common Variable and Combined ...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 073

HHS-HCC 073 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 47

Disorders of Immunity

Code-level coefficient reference

RXHCC

Mapped

HCC 99

Immune Disorders

Code-level coefficient reference

Code Book Path

Official

D81Combined immunodeficiencies

D81.8Other combined immunodeficiencies

D81.89Other combined immunodeficiencies

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for D81.89 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for D81.89 in this effective period.

Related Child Codes

Official

D81.81Biotin-dependent carboxylase deficiency

D81.82Activated Phosphoinositide 3-kinase Delta Syndrome [APDS]

Includes

Official

ICD-10-CM does not list Includes notes for D81.89 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for D81.89 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for D81.89 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for D81.89 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for D81.89 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation must specify the particular combined immunodeficiency diagnosed, including genetic testing results when available, lymphocyte subset analysis, immunoglobulin levels, functional immune testing, and clinical manifestations.

Explain why the condition does not fit other D81.0-D81.82 subcategories.

Document the specific infections and complications managed.

MEAT Support

HCC Buddy guidance

Explain why the condition does not fit other D81.0-D81.82 subcategories.

Document the specific infections and complications managed.

Audit Caution

HCC Buddy guidance

Review all specific D81 subcategories before assigning D81.

This code should only be used when the documented combined immunodeficiency is specified but does not match any existing subcategory. If the type is truly unknown, use D81.9 (unspecified) instead. As new specific codes are added to ICD-10-CM updates, conditions previously coded here may gain their own codes.

Common Mistakes

HCC Buddy guidance

D81.0 through D81.82 (specific combined immunodeficiency subtypes that should be used when applicable), D81.9 (combined immunodeficiency, unspecified, when no specific type is identified), D83.8 (other common variable immunodeficiency for primarily antibody-mediated defects), D84.89 (other immunodeficiencies for non-combined defects).

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is D81.89 an HCC code?

Yes. D81.89 (Other combined immunodeficiencies) maps to HCC 114, Common Variable and Combined Immunodeficiencies under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 2.262. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: D81.89 is billable and maps to V28 HCC 114, Common Variable and Combined Immunodeficiencies. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: D81.89
Description: Other combined immunodeficiencies
HCC (V28): HCC 114 — Common Variable and Combined Immunodeficiencies
RAF reference coefficient: 2.262
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 114, Common Variable and Combined Immunodeficiencies

2.262

ESRDHCC 47, Disorders of Immunity

Not separately weighted

RxHCCHCC 99, Immune Disorders

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work D81.89 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for D81.89

For D81.89 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed D81.89 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

D81.89 is the ICD-10-CM diagnosis code for other combined immunodeficiencies. A rare condition where the immune system is weakened due to multiple genetic defects, but the specific defects do not fit into other defined categories. D81.89 sits in the ICD-10-CM chapter for diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89), within the section covering certain disorders involving the immune mechanism (d80-d89).

Under the CMS-HCC V28 risk adjustment model, D81.89 maps to Common Variable and Combined Immunodeficiencies (HCC 114) with a source-labeled community, non-dual, aged reference coefficient of 2.262. No V24 mapping is shown for D81.89; use the applicable model and payment year when reviewing the V28 mapping. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Use this code for combined immunodeficiencies that are not otherwise specified in categories D81.0-D81.7. Because D81.89 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for D81.89 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code for combined immunodeficiencies that are not otherwise specified in categories D81.0-D81.7
•Document all identified immune defects and associated infections to support medical necessity

Clinical Significance

Other combined immunodeficiencies encompasses a heterogeneous group of primary immunodeficiency disorders affecting both cellular and humoral immunity that do not fit into the specifically defined SCID or other D81 subcategories. These conditions include ZAP-70 deficiency, interleukin-2 receptor deficiency, DOCK8 deficiency, and other rare genetic immunodeficiencies with combined T-cell and B-cell dysfunction.

Documentation Requirements

✓Documentation must specify the particular combined immunodeficiency diagnosed, including genetic testing results when available, lymphocyte subset analysis, immunoglobulin levels, functional immune testing, and clinical manifestations.
✓Explain why the condition does not fit other D81.0-D81.82 subcategories.
✓Document the specific infections and complications managed.

Commonly Confused Codes

•D81.0 through D81.82 (specific combined immunodeficiency subtypes that should be used when applicable), D81.9 (combined immunodeficiency, unspecified, when no specific type is identified), D83.8 (other common variable immunodeficiency for primarily antibody-mediated defects), D84.89 (other immunodeficiencies for non-combined defects).