ICD-10-CM Code D89.40

Mast cell activation, unspecified

Version 2020 Billable Code

Valid for Submission

D89.40 is a billable code used to specify a medical diagnosis of mast cell activation, unspecified. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code D89.40 might also be used to specify conditions or terms like anaphylaxis due to mast cell disorder.

Short Description:Mast cell activation, unspecified
Long Description:Mast cell activation, unspecified

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code D89.40:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Mast cell activation disorder, unspecified
  • Mast cell activation syndrome, NOS

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code D89.40 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Anaphylaxis due to mast cell disorder

Clinical Information

  • MASTOCYTOSIS-. a heterogenous group of disorders characterized by the abnormal increase of mast cells in only the skin mastocytosis cutaneous in extracutaneous tissues involving multiple organs mastocytosis systemic or in solid tumors mastocytoma.

Diagnostic Related Groups

The ICD-10 code D89.40 is grouped in the following groups for version MS-DRG V37.0 What are Diagnostic Related Groups?
The Diagnostic Related Groups (DRGs) are a patient classification scheme which provides a means of relating the type of patients a hospital treats. The DRGs divides all possible principal diagnoses into mutually exclusive principal diagnosis areas referred to as Major Diagnostic Categories (MDC).
applicable from 10/01/2019 through 09/30/2020.


Replacement Code

D8940 replaces the following previously assigned ICD-10 code(s):

  • D89.89 - Oth disrd involving the immune mechanism, NEC

Convert D89.40 to ICD-9

  • 279.8 - Immune mechanism dis NEC (Approximate Flag)

Code Classification

  • Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50–D89)
    • Certain disorders involving the immune mechanism (D80-D89)
      • Oth disorders involving the immune mechanism, NEC (D89)

Code History

  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020