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ICD-10 Guide
ICD-10 CodesD89.4

D89.4

Billable

Mast cell activation syndrome and related disorders

BILLABLE STATUSYes
IMPLEMENTATION DATEOctober 1, 2015
LAST UPDATED09/05/2025

Code Description

ICD-10 D89.4 is a billable code used to indicate a diagnosis of mast cell activation syndrome and related disorders.

Key Diagnostic Point:

Mast cell activation syndrome (MCAS) is a condition characterized by inappropriate and excessive activation of mast cells, leading to a range of symptoms that can affect multiple organ systems. Mast cells are immune cells that play a crucial role in allergic responses and inflammation. In MCAS, mast cells release mediators such as histamine, cytokines, and other inflammatory substances without the typical triggers associated with allergic reactions. This can result in symptoms such as flushing, hives, abdominal pain, diarrhea, and anaphylaxis. The condition can be primary, secondary, or idiopathic, with primary MCAS often associated with clonal mast cell disorders. Diagnosis typically involves clinical evaluation, symptom assessment, and laboratory tests to measure mast cell mediators. Treatment focuses on symptom management and may include antihistamines, mast cell stabilizers, and avoidance of known triggers. Given the complexity of symptoms and the potential overlap with other conditions, accurate diagnosis and coding are essential for effective management and reimbursement.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variety of symptoms that can mimic other conditions
  • Need for thorough documentation of clinical history and symptoms
  • Potential for misdiagnosis with other mast cell disorders
  • Variability in treatment approaches based on individual patient responses

Audit Risk Factors

  • Inadequate documentation of symptoms and triggers
  • Failure to provide laboratory results supporting diagnosis
  • Misclassification of MCAS as an allergic reaction without proper evidence
  • Inconsistent coding practices across different specialties

Specialty Focus

Medical Specialties

Allergy and Immunology

Documentation Requirements

Detailed patient history, symptom diary, and laboratory test results.

Common Clinical Scenarios

Patients presenting with recurrent anaphylaxis or unexplained allergic symptoms.

Billing Considerations

Ensure that all symptoms are documented, including triggers and response to treatments.

Hematology

Documentation Requirements

Complete blood counts, bone marrow biopsy results, and mast cell mediator levels.

Common Clinical Scenarios

Patients with hematologic disorders presenting with mast cell-related symptoms.

Billing Considerations

Document any hematologic abnormalities that may be related to mast cell activation.

Coding Guidelines

Inclusion Criteria

Use D89.4 When
  • Follow the official ICD
  • CM coding guidelines for accurate coding of MCAS
  • Ensure that the diagnosis is supported by clinical documentation and laboratory findings
  • Include any relevant co
  • morbid conditions that may affect treatment

Exclusion Criteria

Do NOT use D89.4 When
No specific exclusions found.

Related ICD-10 Codes

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of MCAS, improving the ability to capture the complexity of the condition and its management. This specificity aids in better understanding and treatment of the disorder.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of MCAS, improving the ability to capture the complexity of the condition and its management. This specificity aids in better understanding and treatment of the disorder.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of MCAS, improving the ability to capture the complexity of the condition and its management. This specificity aids in better understanding and treatment of the disorder.

Resources

Clinical References

  • •
    Mast Cell Activation Syndrome: A Comprehensive Review

Coding & Billing References

  • •
    Mast Cell Activation Syndrome: A Comprehensive Review

Frequently Asked Questions

What are the common symptoms of Mast Cell Activation Syndrome?

Common symptoms include flushing, hives, abdominal pain, diarrhea, and anaphylaxis. Symptoms can vary widely among individuals.