What is ICD-10 code D80.5?

D80.5 is the ICD-10-CM diagnosis code for Immunodeficiency with increased immunoglobulin M [IgM]. A condition where the body has abnormally high levels of IgM antibodies combined with deficiency of other antibody types. D80.5 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. D80.5 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. D80.5 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. D80.5 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 D80.5 map to under V28?

D80.5 maps to CMS-HCC V28 HCC 115 (Specified Immunodeficiencies and White Blood Cell Disorders). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM D80.5: Immunodeficiency

D80.5 maps to CMS-HCC V28 115. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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Code lookupD80.5

Effective 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)

D80.5

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

Immunodeficiency with increased immunoglobulin M [IgM]

A condition where the body has abnormally high levels of IgM antibodies combined with deficiency of other antibody types.

Buddy Insight

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 115

Specified Immunodeficiencies ...

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 074

HHS-HCC 074 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

D80Immunodeficiency with predominantly antibody defects D80.5Immunodeficiency with increased immunoglobulin M [IgM]

Inclusion Terms

Official

No inclusion terms are included in this display for D80.5. 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

D80.0Hereditary hypogammaglobulinemia D80.1Nonfamilial hypogammaglobulinemia D80.2Selective deficiency of immunoglobulin A [IgA]D80.3Selective deficiency of immunoglobulin G [IgG] subclasses D80.4Selective deficiency of immunoglobulin M [IgM]

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

autoimmune disease (systemic) NOS (M35.9)Inherited from D80-D89
functional disorders of polymorphonuclear neutrophils (D71-)Inherited from D80-D89
human immunodeficiency virus [HIV] disease (B20)Inherited from D80-D89

Code First

Official

No Code First sequencing instructions are included in this display for D80.5. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for D80.5. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for D80.5. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documentation must include quantitative immunoglobulin levels showing elevated Immunoglobulin M with reduced Immunoglobulin G and Immunoglobulin A, genetic testing results if available (CD40 ligand or activation-induced cytidine deaminase mutations), clinical manifestations including infection history, neutropenia if present, and treatment including immunoglobulin replacement therapy and prophylactic antimicrobials.

MEAT Support

HCC Buddy guidance

Audit Caution

HCC Buddy guidance

The hallmark of this condition is the inverse pattern: HIGH Immunoglobulin M with LOW Immunoglobulin G and Immunoglobulin A. Do not confuse with D80.4 (selective Immunoglobulin M deficiency) which has the opposite immunoglobulin profile. Elevated Immunoglobulin M can also occur in chronic infections and autoimmune diseases

ensure the elevation is due to a class-switching defect rather than reactive polyclonal Immunoglobulin M elevation.

Common Mistakes

HCC Buddy guidance

D80.4 (selective Immunoglobulin M deficiency which has LOW Immunoglobulin M, the opposite pattern), D80.0 (hereditary hypogammaglobulinemia which has all immunoglobulins low), D81.2 (severe combined immunodeficiency with B-cell numbers preserved but different mechanism), D83.0 (common variable immunodeficiency with B-cell abnormalities, a different entity).

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 D80.5 an HCC code?

Yes. D80.5 (Immunodeficiency with increased immunoglobulin M [IgM]) maps to HCC 115, Specified Immunodeficiencies and White Blood Cell Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.565. 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: D80.5 is billable and maps to V28 HCC 115, Specified Immunodeficiencies and White Blood Cell Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: D80.5
Description: Immunodeficiency with increased immunoglobulin M [IgM]
HCC (V28): HCC 115 — Specified Immunodeficiencies and White Blood Cell Disorders
RAF reference coefficient: 0.565
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 115, Specified Immunodeficiencies and White Blood Cell Disorders

0.565

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 D80.5 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D80.5

For D80.5, 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

D80.5 is the ICD-10-CM diagnosis code for immunodeficiency with increased immunoglobulin m [igm]. A condition where the body has abnormally high levels of IgM antibodies combined with deficiency of other antibody types. D80.5 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, D80.5 maps to Specified Immunodeficiencies and White Blood Cell Disorders (HCC 115) with a source-labeled community, non-dual, aged reference coefficient of 0.565. No V24 mapping is shown for D80.5; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. 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.

This represents a specific immunodeficiency pattern with elevated IgM; document other deficient immunoglobulins. For D80.5, 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. 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 D80.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This represents a specific immunodeficiency pattern with elevated IgM; document other deficient immunoglobulins
•Note any associated infections, autoimmune features, or lymphoid hyperplasia

Clinical Significance

Immunodeficiency with increased immunoglobulin M, also known as hyper-Immunoglobulin M syndrome, is a primary immunodeficiency caused by defective immunoglobulin class switching, resulting in elevated Immunoglobulin M but severely deficient Immunoglobulin G and Immunoglobulin A. Patients are highly susceptible to opportunistic infections including Pneumocystis jirovecii pneumonia, Cryptosporidium enteritis, and recurrent bacterial infections.

Documentation Requirements

✓Documentation must include quantitative immunoglobulin levels showing elevated Immunoglobulin M with reduced Immunoglobulin G and Immunoglobulin A, genetic testing results if available (CD40 ligand or activation-induced cytidine deaminase mutations), clinical manifestations including infection history, neutropenia if present, and treatment including immunoglobulin replacement therapy and prophylactic antimicrobials.

Commonly Confused Codes

•D80.4 (selective Immunoglobulin M deficiency which has LOW Immunoglobulin M, the opposite pattern), D80.0 (hereditary hypogammaglobulinemia which has all immunoglobulins low), D81.2 (severe combined immunodeficiency with B-cell numbers preserved but different mechanism), D83.0 (common variable immunodeficiency with B-cell abnormalities, a different entity).