2027 ICD-10-CM Diagnosis Code D84.1Defects in the complement system
ICD-10-CM Codes›D50–D89›D80-D89›D84
- Billable — Valid for Submission
- Risk Adjusts — HCC 115
- Chronic Condition
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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 642. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.
For Medicare Advantage risk adjustment, D84.1 maps to CMS-HCC Category 115 (Specified Immunodeficiencies and White Blood Cell Disorders) under the V28 model, adding a risk factor of about 0.565 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
D84.1 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
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 infection caused by Gram-negative bacteria
- Recurrent infection caused by Neisseria
- Recurrent Neisseria infection due to factor D deficiency
- Terminal component deficiency
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to D84.1: its own notes plus those printed at block D80-D89 and Chapter 3. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- defects in the complement system
- immunodeficiency disorders, except human immunodeficiency virus [HIV] disease
- sarcoidosis
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- C1 esterase inhibitor [C1-INH] deficiency
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- human immunodeficiency virus [HIV] disease (B20)
- autoimmune disease (systemic) NOS (M35.9)
- certain conditions originating in the perinatal period (P00-P96)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- human immunodeficiency virus [HIV] disease (B20)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name D84.1, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming D84.1: they are not reported together with it, unless the two conditions are unrelated.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Edema, edematous (infectious) (pitting) (toxic) R60.9
angioneurotic (allergic) (any site) (with urticaria) T78.3
hereditary D84.1
hereditary D84.1
hereditary D84.1
glottis, glottic, glottidis (obstructive) (passive) J38.4
hereditary D84.1
hereditary D84.1
hereditary D84.1
hereditary D84.1
with angioneurotic edema T78.3
hereditary D84.1
hereditary D84.1
hereditary D84.1
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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
Code HistoryHistory
Questions About D84.1Overview
What is the ICD-10 code for defects in the complement system?
The ICD-10-CM code for defects in the complement system is D84.1 (sometimes written as D841). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
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, 2026 through September 30, 2027.
What MS-DRG does D84.1 group to?
When defects in the complement system is the principal diagnosis on an inpatient stay, it groups to MS-DRG 642 (inborn and Other Disorders of Metabolism), which carries a relative weight of 1.3226. Higher weights mean higher Medicare reimbursement.
Can D84.1 be reported with M35.9?
Not as a rule. The Excludes1 note at block D80-D89, which applies to D84.1, lists "autoimmune disease (systemic) NOS (M35.9)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
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.
What HCC is D84.1?
D84.1 (defects in the complement system) maps to CMS-HCC Category 115 (Specified Immunodeficiencies and White Blood Cell Disorders), commonly written as HCC 115, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 23 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 98.
Does D84.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, D84.1 adds a risk adjustment factor of about 0.565 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.302 to 0.692 depending on the payment segment). A more severe related category (HCC 114) supersedes it when both are reported. See the full factor table on the HCC 115 category page.
