D81.9 Combined immunodeficiency, unspecified

✓ Billable ICD-10-CM 2026
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The ICD-10-CM code for Combined immunodeficiency, unspecified is D81.9 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Section
D80-D89: Certain disorders involving the immune mechanism (D80-D89)
Category D81
21 codes (17 billable)
FY2026 Status
Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to D81.9:

  • Immunodeficiency › severe combined (SCID)
  • Syndrome › immunity deficiency, combined
  • Syndrome › combined immunity deficiency
  • Immunodeficiency › combined
  • Agammaglobulinemia (acquired (secondary)) (nonfamilial) › lymphopenic
  • Deficiency, deficient › immunity › combined
  • Agammaglobulinemia (acquired (secondary)) (nonfamilial) › with › lymphopenia
  • Immunodeficiency › combined › severe (SCID)

Inclusion Terms

  • Severe combined immunodeficiency disorder [SCID] NOS

U.S. Hospital Utilization

  • An estimated 1,355 U.S. inpatient stays in 2023 included D81.9 among the documented diagnoses.
  • 90 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Chapter 3 TOC entry

3. Chapter 3: Disease of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) ............................................................................................. 39

— ICD-10-CM Official Guidelines for Coding and Reporting, FY2026, Section I.C.3
Reserved for future guideline expansion

Reserved for future guideline expansion ...................................................................................... 39

— ICD-10-CM Official Guidelines for Coding and Reporting, FY2026, Section I.C.3.Reserved

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

Related Codes

Parent Code

D81 Combined immunodeficiencies

Related Codes in D81

D81 Combined immunodeficiencies D81.0 Severe combined immunodeficiency [SCID] with reticular dysgenesis D81.1 Severe combined immunodeficiency [SCID] with low T- and B-cell numbers D81.2 Severe combined immunodeficiency [SCID] with low or normal B-cell numbers D81.3 Adenosine deaminase [ADA] deficiency D81.30 Adenosine deaminase deficiency, unspecified D81.31 Severe combined immunodeficiency due to adenosine deaminase deficiency D81.32 Adenosine deaminase 2 deficiency D81.39 Other adenosine deaminase deficiency D81.4 Nezelof's syndrome D81.5 Purine nucleoside phosphorylase [PNP] deficiency D81.6 Major histocompatibility complex class I deficiency D81.7 Major histocompatibility complex class II deficiency D81.8 Other combined immunodeficiencies D81.81 Biotin-dependent carboxylase deficiency D81.810 Biotinidase deficiency D81.818 Other biotin-dependent carboxylase deficiency D81.819 Biotin-dependent carboxylase deficiency, unspecified D81.82 Activated Phosphoinositide 3-kinase Delta Syndrome [APDS] D81.89 Other combined immunodeficiencies
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Reviewed by Prajwal Shrestha, CPC, CRC
Certified Professional Coder (CPC) and Certified Risk Adjustment Coder (CRC) · AAPC Member ID 01997614 · About · Editorial policy · Content last reviewed: 2025-10-01

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