Neuromyelitis Optica Spectrum Disorder (NMOSD) is an autoimmune disorder characterized by central nervous system (CNS) demyelination, autoantibodies against aquaporin-4 (AQP4-Ab), and a higher prevalence in Asian.^[1] Diagnosis is often challenged due to varying presentations. We report an atypical NMOSD case featuring an unusual cerebral spinal fluid (CSF) profile mimicking CNS infection.

A 22-year-old Asian male was admitted for quadriplegia and lower extremity sensory loss. His cranial nerves were intact. MRI revealed extensive T2 hyperintense lesions in cerebral white matter and throughout the spinal cord (Figure). CSF analysis showed significant pleocytosis (4,225/uL with 90% neutrophils), hypoglycorrhachia (11mg/dL), and elevated protein levels (966mg/dL), concerning for septic myelitis and rhombencephalitis. Despite broad-spectrum anti-microbials, his condition worsened. A comprehensive infectious disease work-up was inconclusive. Repeat CSF studies showed mild pleocytosis and normal glucose. Other testing later revealed positive AQP4-Ab in CSF and serum, with negative MOG-IgG, confirming NMOSD diagnosis. The patient’s treatment involved a multidisciplinary approach with plasmapheresis therapy, pulse-dose steroids, rituximab, and hydroxychloroquine. He exhibited moderate functional improvement and was discharged after 41 days in the hospital with outpatient care and ongoing rehabilitation.

CSF pleocytosis has been observed in NMOSD^[2] but rarely with extreme values. A study reported the highest nucleated cell count being 380/uL in 211 patients.^[2] Hypoglycorrhachia in NMOSD, possibly due to disruption of TCA cycle through pyruvate pathway, is uncommon. A small study showed the mean CSF glucose in NMOSD (74.7 mg/dL) to be mildly lower than healthy controls (82.2 mg/dL) without statistical significance.^[3] Only one previous NMOSD case was reported with extreme CSF pleocytosis (>1000/uL) and hypoglycorrhachia (<20mg/dL).^[4] These unusual CSF markers should not rule out autoimmune diseases from the differentials. Physicians need to maintain a high index of suspicion for NMOSD, especially when presented with ambiguous clinical signs in the acute phase of illness.