ICD-10 Code B27.01 – Gammaherpesviral mononucleosis with polyneuropathy (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B27.01 – Gammaherpesviral mononucleosis with polyneuropathy
What it is
This code identifies infectious mononucleosis caused by a gammaherpesvirus, with associated polyneuropathy. Use it when the record links the viral illness to multiple peripheral nerve symptoms.
Clinical signs
Typical mononucleosis findings may include fever, sore throat, lymph node enlargement, and fatigue. Polyneuropathy can present with symmetric numbness, tingling, weakness, or reduced reflexes; clinical features vary, refer to documentation.
When to use this code
Use B27.01 when the clinician documents gammaherpesviral mononucleosis and a concurrent polyneuropathy, or clearly states the neuropathy is due to the infection. You need documentation that connects both conditions. If the virus type or neurologic complication is not specified, check documentation.
Do not use for
Do not use this code for mononucleosis without nerve involvement, or for neuropathy from another cause. If the record says “infectious mononucleosis” but does not identify a gammaherpesvirus, check documentation.
Coding tip
Confirm both the viral etiology and the neurologic complication are explicitly documented before assigning B27.01.