ICD-10 Code B27.12 – Cytomegaloviral mononucleosis with meningitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B27.12 – Cytomegaloviral mononucleosis with meningitis
What it is
B27.12 identifies mononucleosis caused by cytomegalovirus with meningitis. Use it when the record shows CMV infection and inflammation of the meninges, the membranes around the brain and spinal cord.
Clinical signs
Clinical features vary; refer to documentation. Typical meningitis findings include headache, neck stiffness, fever, photophobia, or altered mental status, along with evidence that CMV is the cause of the mononucleosis syndrome.
When to use this code
Use B27.12 when the clinician documents cytomegaloviral mononucleosis and specifically links meningitis to the infection. It may also apply when the final diagnosis states CMV mononucleosis with meningitis, even if supporting tests are described elsewhere in the chart.
Do not use for
Do not use this code for CMV infection without meningitis, or for meningitis from another organism. If the record only says “viral meningitis” or “mononucleosis” without CMV linkage, check documentation.
Coding tip
Assign B27.12 only when both CMV mononucleosis and meningitis are clearly documented together.