ICD-10-CM 2027
ICD-10 code for complement system defect
From the official ICD-10-CM alphabetic index entry “Defect, defective › complement system”. Page updated September 29, 2026.
About coding complement system defect
The ICD-10-CM code for complement system defect is D84.1 (Defects in the complement system).
Within D84 (other immunodeficiencies), D84.1 is specifically for defects in the complement system. Related codes cover lymphocyte function antigen-1 [LFA-1] defect (D84.0), other specified immunodeficiencies (D84.8) and immunodeficiency, unspecified (D84.9).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 642 (Inborn and Other Disorders of Metabolism, relative weight 1.3219), in MDC 10 (Endocrine, Nutritional and Metabolic Diseases and Disorders), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Common questions about complement system defect ICD-10 codes
What is the ICD-10 code for complement system defect?
- D84.1 — Defects in the complement system.
Is D84.1 billable?
- Yes. D84.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can D84.1 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict D84.1 as a principal diagnosis.
Is D84.1 a CC or MCC?
- No. D84.1 is neither a CC nor an MCC under MS-DRG v44.0.