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

Compare with another code for D84.1Check this code on a claim

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Official instructions
4 inclusion terms · 2 Excludes1 · 1 Excludes2
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 23 · RxHCC V08 category 98

What these terms mean →

Billable · FY2027A valid, specific ICD-10-CM code, reportable for dates of service in FY2027.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

Excludes1from D80-D89Not reported with this code unless documented as unrelated
  • autoimmune disease (systemic) NOS (M35.9)
  • functional disorders of polymorphonuclear neutrophils (D71-)
Excludes2from D80-D89Not included here; may be reported together
  • human immunodeficiency virus [HIV] disease (B20)
IncludesWhat this code covers
  • defects in the complement system (from D80-D89)
  • immunodeficiency disorders, except human immunodeficiency virus [HIV] disease (from D80-D89)
  • sarcoidosis (from D80-D89)
  • C1 esterase inhibitor [C1-INH] deficiency

Where it sits Source: CMS/NCHS

Under:Chapter 3: Diseases of the Blood and Blood-forming Organs and Certain Disorders Involving the Immune MechanismD80-D89 Certain disorders involving the immune mechanismD84 Other immunodeficiencies

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related Codes

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 642 — INBORN AND OTHER DISORDERS OF METABOLISM (MDC 10)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 115 — Specified Immunodeficiencies and White Blood Cell Disorders

Other models: CMS-HCC V22 HCC 23 · RxHCC V08 HCC 98

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for D84.1 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on D84.1 itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • defects in the complement system
  • immunodeficiency disorders, except human immunodeficiency virus [HIV] disease
  • sarcoidosis

Source: inherited from D80-D89

Inclusion Terms

Alternative terms the tabular list files under this code.

  • C1 esterase inhibitor [C1-INH] deficiency

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from D80-D89

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from D80-D89

Coder workflow for D84.1

MedCoder structured workflow — derived from this code’s own official record

Before you code D84.1

  1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with D84.1. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in D84.1’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewM35.9, D71

Consider D84.1. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Official instructions as workflow

  • Excludes1 — check before selecting D84.1(2 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with D84.1: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareM35.9, D71

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of D84.1(1 note)

    Coding workflow: The conditions named in this note are not included in D84.1. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareB20

    See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition D84.1 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewM35.9, D71

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse D84.1 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of D84.1 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • M35.9— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of autoimmune disease (systemic) NOS moves the case to M35.9; the two are not reported together unless documented as unrelated.

    Full comparison: D84.1 vs M35.9 →

  • D71— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of functional disorders of polymorphonuclear neutrophils moves the case to D71; the two are not reported together unless documented as unrelated.

    Full comparison: D84.1 vs D71 →

  • D84.9— Specificity relationship (Review)

    Overlapping diagnoses in the same category.

    Overlapping codes in the same category — the documentation decides which is the more specific fit.

    What moves you there: A record that documents no more than “Immunodeficiency, unspecified” takes D84.9; specificity in the record moves it back here.

    Full comparison: D84.1 vs D84.9 →

  • B20— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of human immunodeficiency virus [HIV] disease adds B20; it is not part of this code and both may be reported when both are documented.

    Full comparison: D84.1 vs B20 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Defects in the complement system is a billable ICD-10-CM diagnosis code (D84.1).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Official Coding Guidelines

No excerpt in the ICD-10-CM Official Guidelines names this code specifically. Its chapter carries only this chapter-wide note:

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

Reserved for future guideline expansion

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name D84.1 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 3 Excludes1 notes across 2 chapters: D72 — Other disorders of white blood cells (via D84.-), D84.81 — Immunodeficiency due to conditions classified elsewhere, L50 — Urticaria.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Code Also instruction: D59.32 — Hereditary hemolytic-uremic syndrome.

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 1 MS-DRG: DRG 642 (MDC 10).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):BLD008 — Immunity disorders (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Specified Immunodeficiencies and White Blood Cell Disorders) for risk-adjusted payment.

D70.0 — Congenital agranulocytosis, D70.4 — Cyclic neutropenia, D71 — Functional disorders of polymorphonuclear neutrophils, D71.1 — Leukocyte adhesion deficiency, D71.8 — Other functional disorders of polymorphonuclear neutrophils, D71.9 — Functional disorders of polymorphonuclear neutrophils, unspecified, D72.0 — Genetic anomalies of leukocytes, D76.1 — Hemophagocytic lymphohistiocytosis, D76.3 — Other histiocytosis syndromes, D80.0 — Hereditary hypogammaglobulinemia, D80.2 — Selective deficiency of immunoglobulin A [IgA], D80.3 — Selective deficiency of immunoglobulin G [IgG] subclasses, D80.4 — Selective deficiency of immunoglobulin M [IgM], D80.5 — Immunodeficiency with increased immunoglobulin M [IgM], D81.4 — Nezelof's syndrome, D82.0 — Wiskott-Aldrich syndrome, D82.1 — Di George's syndrome, D89.84 — IgG4-related disease

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Common Variable and Combined Immunodeficiencies

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Immunity disorders).

D82.3 — Immunodeficiency following hereditary defective response to Epstein-Barr virus, D82.4 — Hyperimmunoglobulin E [IgE] syndrome, D82.8 — Immunodeficiency associated with other specified major defects, D82.9 — Immunodeficiency associated with major defect, unspecified, D83.0 — Common variable immunodeficiency with predominant abnormalities of B-cell numbers and function, D83.1 — Common variable immunodeficiency with predominant immunoregulatory T-cell disorders, D83.2 — Common variable immunodeficiency with autoantibodies to B- or T-cells, D83.8 — Other common variable immunodeficiencies, D83.9 — Common variable immunodeficiency, unspecified, D84.0 — Lymphocyte function antigen-1 [LFA-1] defect, D84.8 — Other specified immunodeficiencies, D84.81 — Immunodeficiency due to conditions classified elsewhere, D84.821 — Immunodeficiency due to drugs, D84.822 — Immunodeficiency due to external causes, D84.89 — Other immunodeficiencies, D84.9 — Immunodeficiency, unspecified, D86.0 — Sarcoidosis of lung, D86.1 — Sarcoidosis of lymph nodes, D86.2 — Sarcoidosis of lung with sarcoidosis of lymph nodes, D86.3 — Sarcoidosis of skin, +64 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Deficiency, deficient”, “Defect, defective”, “Edema, edematous”; these codes share that main term but sit in a different category of the Tabular List.

D81.31 — Severe combined immunodeficiency due to adenosine deaminase deficiency (adenosine deaminase, with severe combined immunodeficiency), D81.32 — Adenosine deaminase 2 deficiency (ADA2), D81.39 — Other adenosine deaminase deficiency (adenosine deaminase, type 1), D81.5 — Purine nucleoside phosphorylase [PNP] deficiency (purine nucleoside phosphorylase), D81.6 — Major histocompatibility complex class I deficiency (major histocompatibility complex, class I), D81.7 — Major histocompatibility complex class II deficiency (major histocompatibility complex, class II), D81.810 — Biotinidase deficiency (biotinidase), D81.819 — Biotin-dependent carboxylase deficiency, unspecified (biotin-dependent carboxylase), D81.9 — Combined immunodeficiency, unspecified (immunity, combined), D82.0 — Wiskott-Aldrich syndrome (immunity, cell-mediated, with thrombocytopenia and eczema), E20.9 — Hypoparathyroidism, unspecified (parathyroid), E23.0 — Hypopituitarism (gonadotropin), E23.2 — Diabetes insipidus (vasopressin), E25.0 — Congenital adrenogenital disorders associated with enzyme deficiency (21-hydroxylase), E27.1 — Primary adrenocortical insufficiency (corticoadrenal, primary), E27.40 — Unspecified adrenocortical insufficiency (corticoadrenal), E27.49 — Other adrenocortical insufficiency (glucocorticoid), E28.39 — Other primary ovarian failure (ovarian), E29.1 — Testicular hypofunction (5-alpha reductase), E31.0 — Autoimmune polyglandular failure (polyglandular, autoimmune), +350 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Alpha-Fetoprotein (AFP) Test, Gamma-glutamyl Transferase (GGT) Test

Contextual Map

Every relationship of D84.1 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run D84.1 with these 4 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Code Also instructions

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 115 — Specified Immunodeficiencies and White Blood Cell Disorders [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 10 — Endocrine, Nutritional and Metabolic Diseases and Disorders[MDC crossing]: “Endocrine, Nutritional and Metabolic Diseases and Disorders — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 5,013 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Index entries (16)

  • Angioedema (allergic) (any site) (with urticaria), hereditary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Angioneurotic edema (allergic) (any site) (with urticaria), hereditary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Bannister's disease, hereditary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Defect, defective, complement system[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Deficiency, deficient, C1 esterase inhibitor (C1-INH)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Edema, edematous (infectious) (pitting) (toxic), angioneurotic (allergic) (any site) (with urticaria), hereditary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Edema, edematous (infectious) (pitting) (toxic), circumscribed, acute, hereditary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Edema, edematous (infectious) (pitting) (toxic), essential, acute, hereditary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • and 8 more

Nearest codes (9)

Change history (3)

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Indexed Clinical Terms (16)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2027), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "D84.1 — Defects in the complement system." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/d84.1-defects-in-the-complement-system

Change history

Changed in FY2027, the release in force: Excludes2 note added; Excludes1 note removed.

  • FY2027 — October 1, 2026
    Excludes2 note added
    human immunodeficiency virus [HIV] disease (B20)
    FY2027 changes
  • FY2027 — October 1, 2026
    Excludes1 note removed
    human immunodeficiency virus [HIV] disease (B20)
    FY2027 changes
  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Defects in the complement system

Nearest Codes in This Family

Official ICD-10-CM classifications closest to D84.1 in its code family, with their registry titles.

View all codes in the D84 family