Case Presentation: A 31-year-old woman with systemic lupus erythematosus (SLE) complicated by class IV nephritis and cutaneous involvement presented with rapidly progressive weakness and urinary retention. She had recently discontinued mycophenolate mofetil for pregnancy planning. Within one week of receiving shingles and pneumococcal vaccines in preparation for azathioprine initiation, she developed ascending numbness and weakness progressing to flaccid quadriparesis. On examination, she required two-person assistance for repositioning, had 0/5 strength in her lower extremities, and exhibited asymmetric upper extremity weakness. Sensation was reduced below the neck without other signs of a lupus flare. MRI showed a longitudinally extensive T2-hyperintense lesion from the cervicomedullary junction to the thoracic cord with patchy enhancement. Cerebrospinal fluid revealed neutrophilic pleocytosis (WBC 4106 cells/µL, 98% neutrophils), elevated protein (688 mg/dL), and negative oligoclonal bands. Repeat testing at a tertiary center confirmed pleocytosis and elevated protein. Serum Aquaporin-4 antibody was positive, confirming neuromyelitis optica spectrum disorder (NMOSD). She received intravenous methylprednisolone for five days, followed by a prednisone taper, seven plasma exchange sessions, and rituximab induction and maintenance therapy. While hospitalized, she worked with PT and OT and was ultimately discharged to inpatient rehab.
Discussion: The coexistence of NMOSD and SLE is uncommon and diagnostically challenging, as both can cause transverse myelitis. Differentiating neuropsychiatric SLE from NMOSD is essential given distinct prognoses and treatments. Longitudinally extensive transverse myelitis (LETM) in patients with SLE should prompt Aquaporin-4 antibody testing, as up to 25% of NMOSD patients have coexisting autoimmune diseases, most commonly SLE. The temporal relationship between vaccination, withdrawal of immunosuppression, and symptom onset suggests immune dysregulation as a potential trigger for NMOSD activation. Acute therapy includes high-dose steroids and plasma exchange; long-term relapse prevention relies on rituximab, azathioprine, mycophenolate, or recently approved targeted agents (eculizumab, inebilizumab, satralizumab). Early recognition is crucial since NMOSD relapse rates exceed 50% in the first year without proper suppressive therapy.Whether NMOSD and SLE represent distinct coexisting autoimmune processes or points along a shared immunologic spectrum remains debated. The presence of Aquaporin-4 antibodies in this case supports NMOSD as a separate disease process, though overlapping immune dysregulation may contribute to their coexistence.
Conclusions: In SLE patients presenting with LETM, early Aquaporin-4 antibody testing is critical to distinguish NMOSD from lupus-related myelitis. Rapid diagnosis and prompt immunosuppression can prevent relapse and reduce the risk of irreversible neurologic disability. This case highlights the importance of early recognition and multidisciplinary collaboration for optimal outcomes.