2026 ICD-10-CM Diagnosis Code D84.1Defects in the complement system

ICD-10-CM Codes›D50–D89›D80-D89›D84

ICD-10-CM D84.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D84.1 is a billable ICD-10-CM diagnosis code for defects in the complement system. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.

Code Identity

ICD-10-CM Code
D84.1
Billable Status
Yes — Valid for Submission
Code Describes
Defects in the complement system
Short Description
Defects in the complement system
Same as the full description in the CMS dataset.
Parent Code
D84
Other 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
CategoryD84Other immunodeficiencies
This CodeD84.1Defects in the complement system

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired angioedema due to C1 inhibitor autoantibody
  • Acquired C1 esterase inhibitor deficiency
  • Alternative pathway deficiency
  • Anaphylotoxin inactivator deficiency
  • Anemia due to mechanical damage
  • Angioedema due to disorder of kinin metabolism
  • Angioedema of gingiva due to deficiency of C1 esterase inhibitor
  • Atypical hemolytic uremic syndrome
  • Atypical hemolytic uremic syndrome with anti-factor H antibodies
  • Atypical hemolytic uremic syndrome with complement gene abnormality
  • Autoimmune angioedema
  • Autoimmune urticaria and/or angioedema
  • Classical complement pathway abnormality
  • Combined complement 6 and 7 deficiencies
  • Complement 1q beta chain deficiency
  • Complement 1q deficiency
  • Complement 1q dysfunction
  • Complement 1r deficiency
  • Complement 1s deficiency
  • Complement 2 deficiency
  • Complement 4 binding protein deficiency
  • Complement 4 deficiency
  • Complement 4A deficiency
  • Complement 4B deficiency
  • Complement 5 deficiency
  • Complement 5 dysfunction
  • Complement 5a inhibitor deficiency
  • Complement 6 deficiency
  • Complement 7 deficiency
  • Complement 8 alpha-gamma deficiency
  • Complement 8 beta chain deficiency
  • Complement 8 beta chain dysfunction
  • Complement 9 deficiency
  • Complement abnormality
  • Complement component 3 deficiency
  • Complement component 8 deficiency
  • Complement component deficiency
  • Complement deficiency disease
  • Complement hyperactivation, angiopathic thrombosis, protein losing enteropathy syndrome
  • Complement receptor 1 deficiency
  • Complement receptor 3 deficiency
  • Complement receptor deficiency
  • Complement regulatory factor defect
  • Coombs negative hemolytic anemia
  • Cutis laxa with complement deficiency
  • Cutis laxa, acquired type
  • Decay accelerating factor deficiency
  • Disorder of complement
  • Edema of oral soft tissues
  • Factor B deficiency
  • Factor D deficiency
  • Factor H deficiency
  • Familial C3B inhibitor deficiency syndrome
  • Gingival edema
  • Glomerular disease due to complement system disorder
  • Hereditary angioedema
  • Hereditary angioedema with C1Inh deficiency
  • Hereditary C1 esterase inhibitor deficiency - deficient factor
  • Hereditary C1 esterase inhibitor deficiency - dysfunctional factor
  • Homologous restriction factor deficiency
  • Immunodeficiency due to MASP-2 deficiency
  • Panniculitis due to immunological disorder
  • Panniculitis with complement deficiency
  • Primary CD59 deficiency
  • Properdin deficiency disease
  • Protein-losing enteropathy
  • Recurrent bacterial infection
  • Recurrent Neisseria infection due to factor D deficiency
  • Terminal component deficiency

Tabular List NotesGuidance

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

Inclusion Terms

  • C1 esterase inhibitor C1-INH deficiency

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.

    • Angioedema(allergic) (any site) (with urticaria)
      • hereditary
    • Angioneurotic edema(allergic) (any site) (with urticaria)
      • hereditary
    • Bannister's disease
      • hereditary
    • Defect, defective
      • complement system
    • Deficiency, deficient
      • C1 esterase inhibitor (C1-INH)
    • Edema, edematous(infectious) (pitting) (toxic)
      • angioneurotic (allergic) (any site) (with urticaria)
        • hereditary
    • Edema, edematous(infectious) (pitting) (toxic)
      • circumscribed, acute
        • hereditary
    • Edema, edematous(infectious) (pitting) (toxic)
      • essential, acute
        • hereditary
    • Edema, edematous(infectious) (pitting) (toxic)
      • glottis, glottic, glottidis (obstructive) (passive)
        • allergic
          • hereditary
    • Edema, edematous(infectious) (pitting) (toxic)
      • periodic
        • hereditary
    • Edema, edematous(infectious) (pitting) (toxic)
      • Quincke's
        • hereditary
    • Giant
      • urticaria
        • hereditary
    • Quincke's disease or edema
      • hereditary
    • Urticaria
      • with angioneurotic edema
        • hereditary
    • Urticaria
      • giant
        • hereditary
    • Urticaria
      • larynx
        • hereditary

Clinical ClassificationClinical

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

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

Clinical InformationClinical

  • Atypical Hemolytic Uremic Syndrome

    an hereditary hemolytic uremic syndrome associated with variations in the gene that encodes complement factor h, or the related proteins cfhr1 and cfhr3. disease often progresses to chronic kidney failure without the prodromal symptoms of enterocolitis and diarrhea that characterize typical hemolytic uremic syndrome.

  • Hereditary Angioedema

    autosomal dominant inherited disorder characterized by abnormalities of c1 inhibitor. patients present with swelling of the skin, subcutaneous tissues, and mucosa sites.

  • Hereditary Angioedema Types I and II

    autosomal dominant inherited disorders characterized by abnormalities of c1 inhibitor. patients present with swelling of the skin, subcutaneous tissues, and mucosa sites. in type i hereditary angioedema, the plasma levels of c1 inhibitor are decreased. in type ii hereditary angioedema, the c1 inhibitor is dysfunctional and its plasma levels may be normal or elevated.

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 D84.1 to ICD-9-CMHistory

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

ICD-9-CM
277.6 Defic circul enzyme NEC
Approximate The match is approximate rather than exact.
ICD-9-CM
279.8 Immune mechanism dis NEC
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 D84.1Overview

Is D84.1 (Other immunodeficiencies) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report defects in the complement system on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of D84.1?

Under the General Equivalence Mappings, defects in the complement system converts to ICD-9-CM 277.6 (defic circul enzyme NEC) and 279.8 (immune mechanism dis NEC). 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.