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v1.0.0
ICD-10 Guide
ICD-10 CodesD89.42

D89.42

Billable

Idiopathic mast cell activation syndrome

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

Code Description

ICD-10 D89.42 is a billable code used to indicate a diagnosis of idiopathic mast cell activation syndrome.

Key Diagnostic Point:

Idiopathic mast cell activation syndrome (IMCAS) is a hematologic condition characterized by recurrent episodes of mast cell activation without an identifiable cause. Patients may experience a range of symptoms, including flushing, abdominal pain, diarrhea, and anaphylaxis-like reactions. The condition is often associated with an increase in mast cells in the bone marrow and other tissues, leading to the release of mediators such as histamine and cytokines. Diagnosis is typically made through clinical evaluation, symptom history, and sometimes bone marrow biopsy to assess mast cell proliferation. IMCAS can significantly impact the quality of life due to its unpredictable nature and the potential for severe allergic reactions. Management often involves the use of antihistamines, mast cell stabilizers, and avoidance of known triggers. Understanding the complexities of IMCAS is crucial for accurate coding and appropriate patient management.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variability in symptom presentation among patients
  • Need for comprehensive patient history to establish diagnosis
  • Potential overlap with other mast cell disorders
  • Requirement for specialist evaluation for accurate diagnosis

Audit Risk Factors

  • Inadequate documentation of symptoms and episodes
  • Failure to document the idiopathic nature of the condition
  • Misclassification with other mast cell disorders
  • Lack of specialist consultation notes

Specialty Focus

Medical Specialties

Allergy and Immunology

Documentation Requirements

Detailed patient history, symptom diary, and results from allergy testing.

Common Clinical Scenarios

Patients presenting with recurrent anaphylaxis or unexplained allergic symptoms.

Billing Considerations

Ensure documentation reflects the idiopathic nature and excludes other conditions.

Hematology

Documentation Requirements

Bone marrow biopsy results, mast cell counts, and clinical symptom correlation.

Common Clinical Scenarios

Patients with elevated mast cell levels and unexplained symptoms.

Billing Considerations

Document the rationale for bone marrow biopsy and any findings related to mast cell proliferation.

Coding Guidelines

Inclusion Criteria

Use D89.42 When
  • Follow the official ICD
  • CM coding guidelines, ensuring that the diagnosis is supported by clinical documentation
  • Include details of recurrent episodes and any relevant laboratory findings

Exclusion Criteria

Do NOT use D89.42 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

85025CPT Code

Complete blood count (CBC) with differential

Clinical Scenario

Used to evaluate mast cell levels and rule out other hematologic conditions.

Documentation Requirements

Document the reason for the CBC and any abnormal findings.

Specialty Considerations

Allergy and Immunology specialists should correlate CBC results with clinical symptoms.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of conditions like IMCAS, improving the accuracy of patient records and facilitating better management of the condition.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of conditions like IMCAS, improving the accuracy of patient records and facilitating better management of the condition.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of conditions like IMCAS, improving the accuracy of patient records and facilitating better management of the condition.

Resources

Clinical References

  • •
    Mast Cell Activation Syndrome Foundation

Coding & Billing References

  • •
    Mast Cell Activation Syndrome Foundation

Frequently Asked Questions

What are the common symptoms of Idiopathic mast cell activation syndrome?

Common symptoms include flushing, abdominal pain, diarrhea, fatigue, and anaphylaxis-like reactions. Symptoms can vary widely among individuals.