Neuromyelitis Optica Spectrum Disorder (NMOSD) is a rare, relapsing autoimmune disease of the central nervous system mediated by IgG autoantibodies against aquaporin-4 (AQP-4-IgG) that mainly affects the optic nerves and spinal cord, commonly manifesting as optic neuritis and transverse myelitis. NMOSD is associated with systemic complications, including venous thromboembolism (VTE), particularly during immobility or active inflammation.

A 38-year-old obese, sedentary woman presented to our emergency department (ED) with progressively worsening bilateral leg weakness for 2 months. One week prior, she presented to an outside ED with right leg swelling and tenderness, found to have a right posterior tibial vein thrombus and discharged on Apixaban. Three days later, patient noted heavier legs, and one day prior to admission, noted inability to move her legs and urinary incontinence. On examination, patient was afebrile, alert and oriented x4. Evaluation of the lower extremities showed absent sensations, right leg strength +1 and left leg 0, deep tendon reflexes +1 bilaterally. Basic labs unrevealing however erythrocyte sedimentation rate and c-reactive protein were elevated. MRI brain and spine showed hyperintensities from C6-T7 concerning for demyelination. Lumbar puncture revealed 13 WBCs, oligoclonal bands, and elevated CSF IgG. Neurology recommended CSF studies revealing AQP-4-IgG with titer 1:320. She was treated with 5 days of intravenous methylprednisolone with no improvement. She was subsequently treated with 4 days of plasma exchange with mild improvement: sensations diminished, left leg +2, right leg +3. She was then started on Ravulizumab and discharged to the Acute Rehab Unit for 5 weeks of intense physical therapy. After 3 weeks, she was able to ambulate with a walker.

This case illustrates NMOSD complicated by DVT in the setting of obesity and sedentary lifestyle, highlighting the increased risk of VTE. Awareness of this association supports early mobilization and appropriate thromboprophylaxis in acute relapses.