Objectives To describe a rare case of double antibody positive Neuromyelitis Optica Spectrum Disorder (NMOSD) with both Aquaporin-4 and MOG antibodies, occurring following a Pertussis infection in a patient with a history of auto-immunity.

Methods Retrospective review of clinical records.

Results A 41-year-old Chinese woman with a history of Systemic Lupus Erythematosus presented with a sub-acute onset of progressive gait ataxia and urinary retention occurring seven days after a confirmed Bordetella pertussis infection. Magnetic resonance imaging revealed extensive subcortical and thalamic T2/FLAIR hyperintensities with subtle enhancement, and a longitudinally extensive non-enhancing spinal cord lesion (T1-T7), without optic nerve involvement. Cerebrospinal fluid protein was raised (0.55 g/L) with 7 mononuclear cells and matched oligoclonal bands. Viral PCRs were negative including JC virus and Pertussis. Established live cell-based immunoassays revealed positivity for both Aquaporin-4 antibodies (in CSF and serum) and MOG antibodies in high titres. Our patient meets the 2015 Consensus Diagnostic Criteria for NMOSD.¹ Treatment with high dose corticosteroids and rituximab lead to clinical and radiological improvement, but she had a clinical relapse 10 months later with new LETM (T3-T7), necessitating increased immunosuppression with more rigorous rituximab dosing of 1000mg every 6 months.

Conclusions Double positivity for both Aquaporin-4 and MOG antibodies in NMOSD is rare. We describe a case of double-positive NMOSD occurring following an infective illness. This case demonstrates that NMOSD may occasionally masquerade as post-infectious Acute Disseminated Encephalomyelitis and highlights the importance of checking antibodies in these patients, given the treatment strategies and risk of relapse differs considerably.