ICD-10-CM 2027
ICD-10 code for immune disease
From the official ICD-10-CM alphabetic index entry “Disease, diseased › immune”. Page updated September 29, 2026.
About coding immune disease
The ICD-10-CM code for immune disease is D89.9 (Disorder involving the immune mechanism, unspecified).
Within D89, choose D89.9 (Disorder involving the immune mechanism, unspecified) only when documentation doesn't support a more specific option: Polyclonal hypergammaglobulinemia (D89.0), Cryoglobulinemia (D89.1), hypergammaglobulinemia, unspecified (D89.2), immune reconstitution syndrome (D89.3), mast cell activation syndrome and related disorders (D89.4) and other specified disorders involving the immune mechanism, not elsewhere classified (D89.8).
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 814 (Reticuloendothelial and Immunity Disorders with MCC, relative weight 2.0729), DRG 815 (Reticuloendothelial and Immunity Disorders with CC, relative weight 1.0444) and DRG 816 (Reticuloendothelial and Immunity Disorders without CC/MCC, relative weight 0.7381), in MDC 16 (Diseases and Disorders of the Blood and Blood Forming Organs and Immunological 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 immune disease ICD-10 codes
What is the ICD-10 code for immune disease?
- D89.9 — Disorder involving the immune mechanism, unspecified.
Is D89.9 billable?
- Yes. D89.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can D89.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict D89.9 as a principal diagnosis.
Is D89.9 a CC or MCC?
- No. D89.9 is neither a CC nor an MCC under MS-DRG v44.0.