Pleocytosis

An abnormal increase in the number of leukocytes within a body fluid, most commonly cerebrospinal fluid (≥5 WBC/μL).

Causes

• Infectious causes

  • Viral meningitis: HSV, West Nile virus, Enteroviruses

  • Viral encephalitis

  • Bacterial meningitis

  • Brain abscess

  • Tuberculosis involving the central nervous system

  • Fungal infections: Cryptococcosis, Histoplasmosis

• Autoimmune and inflammatory causes

  • Multiple sclerosis

  • Autoimmune encephalitis

  • Sarcoidosis

  • Systemic lupus erythematosus (SLE)

  • Sjögren’s syndrome

• Malignant causes

  • Leukemia with central nervous system involvement

  • Lymphoma

  • Metastatic cancer involving the meninges (leptomeningeal carcinomatosis)

• Subarachnoid hemorrhage

• Medicatios causing aseptic inflammatory reactions: NSAIDs, Antibiotics

• Other causes

  • Chemical meningitis

  • Post-neurosurgical inflammation

  • Traumatic lumbar puncture (blood contamination of cerebrospinal fluid)