Pleocytosis

An abnormal increase in the number of leukocytes within a body fluid, most commonly cerebrospinal fluid (≥5 WBC/μL). Possible causes are viral meningitis/encephalitis (HSV, West Nile, enteroviruses), bacterial meningitis, brain abscess, tuberculosis, fungal infection (cryptococcal, histoplasmosis), autoimmune inflammation (multiple sclerosis, autoimmune encephalitis, sarcoidosis, lupus, or Sjögren's syndrome), malignancy (metastasis, leukemia, lymphoma), subarachnoid hemorrhage, or medications (NSAIDs, antibiotics).