2026 ICD-10-CM Diagnosis Code D81.9Combined immunodeficiency, unspecified

ICD-10-CM Codes›D50–D89›D80-D89›D81

ICD-10-CM D81.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D81.9 is a billable ICD-10-CM diagnosis code for combined immunodeficiency, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 808 through 810. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.

Code Identity

ICD-10-CM Code
D81.9
Billable Status
Yes — Valid for Submission
Code Describes
Combined immunodeficiency, unspecified
Short Description
Combined immunodeficiency, unspecified
Same as the full description in the CMS dataset.
Parent Code
D81
Combined immunodeficiencies

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
CategoryD81Combined immunodeficiencies
This CodeD81.9Combined immunodeficiency, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Autoimmune hemolytic anemia, autoimmune thrombocytopenia, primary immunodeficiency syndrome
  • Autosomal recessive SCID
  • Benign combined immunodeficiency
  • Combined immunodeficiency disease
  • Combined immunodeficiency with faciooculoskeletal anomalies syndrome
  • Combined immunodeficiency with granulomatosis
  • Congenital atrophy of optic nerve
  • Hepatic veno-occlusive disease with immunodeficiency syndrome
  • Obstruction of visceral vein
  • Severe combined immunodeficiency disease
  • Severe combined immunodeficiency with low T- and B-cell numbers
  • Severe combined immunodeficiency with maternofetal engraftment
  • Severe combined immunodeficiency, microcephaly, growth retardation, sensitivity to ionizing radiation syndrome
  • Short-limb skeletal dysplasia with severe combined immunodeficiency
  • Veno-occlusive disease of the liver

Tabular List NotesGuidance

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

Inclusion Terms

  • Severe combined immunodeficiency disorder SCID NOS

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

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

Clinical ClassificationClinical

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

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

Patient EducationClinical

Immune System and Disorders

Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.

The full article covers:

  • What is the immune system?
  • What are the parts of the immune system?
  • How does the immune system work?
  • What are the types of immunity?
  • What can go wrong with the immune system?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert D81.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
279.2 Combined immunity defic
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About D81.9Overview

Is D81.9 (Combined immunodeficiencies) a billable code?

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

What MS-DRG does D81.9 group to?

When combined immunodeficiency, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 808, 809, 810, with relative weights from 1.0466 to 2.2079 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of D81.9?

Under the General Equivalence Mappings, combined immunodeficiency, unspecified converts to ICD-9-CM 279.2 (combined immunity defic). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.