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D84.81 ICD-10-CM Code: Immunodeficiency due to conditions classified elsewhere

D84.81 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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Code lookupD84.81

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)

D84.81

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

Immunodeficiency due to conditions classified elsewhere

A weakened immune system that develops as a result of another medical condition or disease the patient already has.

Buddy the Bee presenting code insight

Buddy Insight

Immunodeficiency due to conditions classified elsewhere represents secondary immunodeficiency that develops as a consequence of another documented medical condition.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

N/A

—

Not mapped

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 074

Code-level coefficient reference

ESRD/PACE

HCC 47

Code-level coefficient reference

RXHCC

HCC 99

Code-level coefficient reference

Code Book Path

Official
D84Other immunodeficienciesD84.8Other specified immunodeficienciesD84.81Immunodeficiency due to conditions classified elsewhere

Inclusion Terms

Official

No inclusion terms are included in this display for D84.81. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • autoimmune disease (systemic) NOS (M35.9)Inherited from D50-D89
  • certain conditions originating in the perinatal period (P00-P96)Inherited from D50-D89
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from D50-D89
  • congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from D50-D89
  • endocrine, nutritional and metabolic diseases (E00-E88)Inherited from D50-D89
  • human immunodeficiency virus [HIV] disease (B20)Inherited from D50-D89
  • injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from D50-D89
  • neoplasms (C00-D49)Inherited from D50-D89
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from D50-D89

Related Codes

Official
D84.82Immunodeficiency due to drugs and external causesD84.89Other immunodeficiencies

Includes

Official
  • defects in the complement systemInherited from D80-D89
  • immunodeficiency disorders, except human immunodeficiency virus [HIV] diseaseInherited from D80-D89
  • sarcoidosisInherited from D80-D89

Excludes 1

Official
  • certain disorders involving the immune mechanism (D80-D83, D84.0, D84.1, D84.9)
  • human immunodeficiency virus [HIV] disease (B20)Inherited from D80-D89
  • autoimmune disease (systemic) NOS (M35.9)Inherited from D80-D89
  • functional disorders of polymorphonuclear neutrophils (D71-)Inherited from D80-D89

Code First

Official
  • underlying condition, such as:
  • chromosomal abnormalities (Q90-Q99)
  • diabetes mellitus (E08-E13)
  • malignant neoplasms (C00-C96)

Use Additional

Official

No Use Additional Code instructions are included in this display for D84.81. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for D84.81. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Documentation must identify and code the underlying condition causing the immunodeficiency (malignancy, renal disease, etc.) as the primary diagnosis, with D84.81 assigned as a secondary code.
Include evidence of immune impairment (recurrent infections, low immunoglobulin levels, abnormal lymphocyte counts) and the causal link between the underlying condition and the immunodeficiency.

MEAT Support

HCC Buddy guidance
Documentation must identify and code the underlying condition causing the immunodeficiency (malignancy, renal disease, etc.) as the primary diagnosis, with D84.81 assigned as a secondary code.
Include evidence of immune impairment (recurrent infections, low immunoglobulin levels, abnormal lymphocyte counts) and the causal link between the underlying condition and the immunodeficiency.

Audit Caution

HCC Buddy guidance
This is a manifestation code requiring an underlying condition to be coded first
never assign D84.81 without the primary causative condition. Do not use this code when the immunodeficiency is drug-related (use D84.821) or due to external causes (use D84.822). The underlying condition must be a recognized cause of immunodeficiency, not simply a comorbidity in a patient who happens to have infections.

Common Mistakes

HCC Buddy guidance
D84.821 (immunodeficiency due to drugs, which is medication-related rather than disease-related), D84.822 (immunodeficiency due to external causes like radiation), D84.89 (other immunodeficiencies when the cause is not another classified condition), D84.9 (immunodeficiency, unspecified, which does not establish causation).

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 D84.81 an HCC code?

D84.81 is not in the CMS-HCC V28 or V24 community payment model. D84.81 has a separate mapping under the CMS-HCC ESRD model (HCC 47 (Disorders of Immunity)) and the Part D RxHCC model (HCC 99 (Immune Disorders)); the applicable result needs member context. D84.81 also appears in the HHS-HCC commercial risk model (HCC 074 (HHS-HCC 074 adult, RAF varies by metal level)), which is a commercial market model rather than a Medicare Advantage payment mapping.

Code
D84.81
Description
Immunodeficiency due to conditions classified elsewhere
HCC (V28)
No CMS-HCC V28 mapping
RAF reference coefficient
—
Billable
Yes
Payment year
2026

HCC Category Mapping

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 D84.81 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D84.81

For D84.81, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

D84.81 is the ICD-10-CM diagnosis code for immunodeficiency due to conditions classified elsewhere. A weakened immune system that develops as a result of another medical condition or disease the patient already has. D84.81 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).

D84.81 has no mapping under the CMS-HCC V28 or V24 community payment models. D84.81 has a separate mapping under the CMS-HCC ESRD model (HCC 47 (Disorders of Immunity)) and the Part D RxHCC model (HCC 99 (Immune Disorders)); the applicable result needs member context. D84.81 also appears in the HHS-HCC commercial risk model (HCC 074 (HHS-HCC 074 adult, RAF varies by metal level)), which is a commercial market model rather than a Medicare Advantage payment mapping. Do not assign V28 risk adjustment value from this page; verify the applicable model and payment year before using this code for risk adjustment.

Always code the underlying condition first, then use this code as a secondary diagnosis.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for D84.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Always code the underlying condition first, then use this code as a secondary diagnosis
  • •Common underlying causes include malignancy, chronic kidney disease, and autoimmune disorders

Clinical Significance

Immunodeficiency due to conditions classified elsewhere represents secondary immunodeficiency that develops as a consequence of another documented medical condition. Common underlying causes include malignancies (particularly lymphoproliferative disorders), chronic kidney disease with uremia, diabetes mellitus, hepatic cirrhosis, and protein-losing enteropathy, all of which impair immune function through different mechanisms.

Documentation Requirements

  • ✓Documentation must identify and code the underlying condition causing the immunodeficiency (malignancy, renal disease, etc.) as the primary diagnosis, with D84.81 assigned as a secondary code.
  • ✓Include evidence of immune impairment (recurrent infections, low immunoglobulin levels, abnormal lymphocyte counts) and the causal link between the underlying condition and the immunodeficiency.

Excludes 1, Do NOT code together

  • certain disorders involving the immune mechanism (D80-D83, D84.0, D84.1, D84.9)
  • human immunodeficiency virus [HIV] disease (B20)

Code First

  • underlying condition, such as:
  • chromosomal abnormalities (Q90-Q99)
  • diabetes mellitus (E08-E13)
  • malignant neoplasms (C00-C96)

Commonly Confused Codes

  • •D84.821 (immunodeficiency due to drugs, which is medication-related rather than disease-related), D84.822 (immunodeficiency due to external causes like radiation), D84.89 (other immunodeficiencies when the cause is not another classified condition), D84.9 (immunodeficiency, unspecified, which does not establish causation).

Child Codes

D84.81Immunodeficiency due to conditions classified elsewhere
D84.82Immunodeficiency due to drugs and external causes
D84.89Other immunodeficiencies

Code Hierarchy

└D84Other immunodeficiencies└D84.8Other specified immunodeficiencies└D84.81Immunodeficiency due to conditions classified elsewhere
└D84.81Immunodeficiency due to conditions classified elsewhere

D84.81 code history

Code setChange
FY2021 (effective Oct 1, 2020)Added to the code set

Source: official CMS ICD-10-CM order and addenda files, FY2016 through FY2027.

Also searched as

  • D84 81
  • D8481

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