D89.4 Mast cell activation syndrome and related disorders

⚠ Non-Billable ICD-10-CM 2026
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The ICD-10-CM code for Mast cell activation syndrome and related disorders is D89.4 (FY2026). It is a non-billable category code — select a more specific code below for claims.

Classification

Section
D80-D89: Certain disorders involving the immune mechanism (D80-D89)
Category D89
29 codes (24 billable)
FY2026 Status
Stable since FY2024
Excludes1
Not coded here. These conditions should NOT be coded together with D89.4.
  • aggressive systemic mastocytosis (C96.21)
  • congenital cutaneous mastocytosis (Q82.2)
  • (non-congenital) cutaneous mastocytosis (D47.01)
  • (indolent) systemic mastocytosis (D47.02)
  • malignant mast cell neoplasm (C96.2-)
  • malignant mastocytoma (C96.29)
  • mast cell leukemia (C94.3-)
  • mast cell sarcoma (C96.22)
  • mastocytoma NOS (D47.09)
  • other mast cell neoplasms of uncertain behavior (D47.09)
  • systemic mastocytosis associated with a clonal hematologic non-mast cell lineage disease (SM-AHNMD) (D47.02)

Official Coding Guidelines

Chapter 3 TOC entry

3. Chapter 3: Disease of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) ............................................................................................. 39

— ICD-10-CM Official Guidelines for Coding and Reporting, FY2026, Section I.C.3
Reserved for future guideline expansion

Reserved for future guideline expansion ...................................................................................... 39

— ICD-10-CM Official Guidelines for Coding and Reporting, FY2026, Section I.C.3.Reserved

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

Related Codes

Parent Code

D89 Other disorders involving the immune mechanism, not elsewhere classified

More Specific Codes

D89.40 Mast cell activation, unspecified D89.41 Monoclonal mast cell activation syndrome D89.42 Idiopathic mast cell activation syndrome D89.43 Secondary mast cell activation D89.44 Hereditary alpha tryptasemia D89.49 Other mast cell activation disorder

Related Codes in D89

D89 Other disorders involving the immune mechanism, not elsewhere classified D89.0 Polyclonal hypergammaglobulinemia D89.1 Cryoglobulinemia D89.2 Hypergammaglobulinemia, unspecified D89.3 Immune reconstitution syndrome D89.40 Mast cell activation, unspecified D89.41 Monoclonal mast cell activation syndrome D89.42 Idiopathic mast cell activation syndrome D89.43 Secondary mast cell activation D89.44 Hereditary alpha tryptasemia D89.49 Other mast cell activation disorder D89.8 Other specified disorders involving the immune mechanism, not elsewhere classified D89.81 Graft-versus-host disease D89.810 Acute graft-versus-host disease D89.811 Chronic graft-versus-host disease D89.812 Acute on chronic graft-versus-host disease D89.813 Graft-versus-host disease, unspecified D89.82 Autoimmune lymphoproliferative syndrome [ALPS] D89.83 Cytokine release syndrome D89.831 Cytokine release syndrome, grade 1
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Reviewed by Prajwal Shrestha, CPC, CRC
Certified Professional Coder (CPC) and Certified Risk Adjustment Coder (CRC) · AAPC Member ID 01997614 · About · Editorial policy · Content last reviewed: 2025-10-01

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