Neuromyelitis Optica Spectrum Disorder Presenting With Longitudinally Extensive Transverse Myelitis and Pontine Involvement in a Patient With Systemic Lupus Erythematosus.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune demyelinating condition of the central nervous system that may coexist with systemic lupus erythematosus (SLE), complicating diagnosis and management. We describe a woman in her 40s with long-standing SLE who presented with acute urinary retention, bilateral lower limb weakness, and diplopia following a febrile illness after unsuccessful in-vitro fertilization (IVF). Initial assessment suggested urinary tract infection, but rapid neurological deterioration prompted MRI, which revealed longitudinally extensive transverse myelitis (LETM) extending from T9 to the conus medullaris and pontine lesions with contrast enhancement. Cerebrospinal fluid analysis showed marked lymphocytic pleocytosis, and the diagnosis of NMOSD was favored. The patient received high-dose intravenous methylprednisolone followed by transfer for plasma exchange (PLEX). This case highlights the diagnostic overlap between SLE and NMOSD and emphasizes the importance of early recognition, imaging, and immunosuppressive therapy to prevent irreversible neurological sequelae.