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v1.0.0
ICD-10 Guide
ICD-10 CodesB27.9

B27.9

Infectious mononucleosis, unspecified

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

Code Description

ICD-10 B27.9 is a billable code used to indicate a diagnosis of infectious mononucleosis, unspecified.

Key Diagnostic Point:

Infectious mononucleosis, commonly known as mono, is primarily caused by the Epstein-Barr virus (EBV), a member of the herpes virus family. This viral infection is characterized by fever, sore throat, swollen lymph nodes, and fatigue. The condition is most prevalent among adolescents and young adults, although it can occur at any age. Diagnosis is typically made through clinical evaluation and serological testing, including heterophile antibody tests (e.g., the Monospot test) and specific EBV antibody tests. While most cases are self-limiting, complications can arise, such as splenic rupture or secondary infections. Treatment is generally supportive, focusing on symptom relief, as there are no specific antiviral therapies approved for EBV. Patients are advised to rest, stay hydrated, and manage pain with over-the-counter medications. The unspecified nature of this code indicates that the specific viral etiology has not been determined or documented, which can complicate treatment and management.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variability in clinical presentation and symptoms.
  • Need for serological testing to confirm diagnosis.
  • Potential for misdiagnosis with other viral infections.
  • Documentation requirements for specifying the viral cause.

Audit Risk Factors

  • Insufficient documentation of symptoms and clinical findings.
  • Lack of serological test results in the medical record.
  • Inconsistent coding of related conditions.
  • Failure to document the duration and severity of symptoms.

Specialty Focus

Medical Specialties

Primary Care

Documentation Requirements

Thorough documentation of symptoms, physical examination findings, and any laboratory tests performed.

Common Clinical Scenarios

Patients presenting with fatigue, sore throat, and lymphadenopathy.

Billing Considerations

Ensure that all relevant tests are documented to support the diagnosis.

Infectious Disease

Documentation Requirements

Detailed history of exposure, comprehensive lab results, and follow-up care notes.

Common Clinical Scenarios

Patients with recurrent symptoms or complications from mononucleosis.

Billing Considerations

Consideration of differential diagnoses and potential complications.

Coding Guidelines

Inclusion Criteria

Use B27.9 When
  • 10 coding guidelines specify that B27
  • 9 should be used when the diagnosis of infectious mononucleosis is made but the specific viral cause is not documented
  • Coders should ensure that all relevant clinical information is captured to support the diagnosis

Exclusion Criteria

Do NOT use B27.9 When
No specific exclusions found.

Related CPT Codes

86790CPT Code

EBV antibody test

Clinical Scenario

When serological testing is performed to confirm EBV infection.

Documentation Requirements

Document the reason for the test and the results.

Specialty Considerations

Infectious disease specialists may require additional tests to rule out other infections.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of infectious mononucleosis, improving the accuracy of data collection and reimbursement processes. B27.9 provides a mechanism for capturing cases where the specific viral cause is not documented.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of infectious mononucleosis, improving the accuracy of data collection and reimbursement processes. B27.9 provides a mechanism for capturing cases where the specific viral cause is not documented.

Reimbursement & Billing Impact

reimbursement processes. B27.9 provides a mechanism for capturing cases where the specific viral cause is not documented.

Resources

Clinical References

  • •
    CDC - Infectious Mononucleosis

Coding & Billing References

  • •
    CDC - Infectious Mononucleosis

Frequently Asked Questions

What are the common symptoms of infectious mononucleosis?

Common symptoms include fever, sore throat, swollen lymph nodes, and fatigue. Some patients may also experience headaches, rash, and splenomegaly.

How is infectious mononucleosis diagnosed?

Diagnosis is typically made through clinical evaluation and serological testing, including the Monospot test and specific EBV antibody tests.

What is the treatment for infectious mononucleosis?

Treatment is primarily supportive, focusing on rest, hydration, and pain relief. There are no specific antiviral treatments for EBV.