PRESENTATION: The patient presented with acute urinary retention, fever (39°C), and rapidly progressive bilateral lower limb weakness progressing to flaccid paraplegia (0/5 MRC) with a T6 sensory level. DIAGNOSIS: MRI spine demonstrated longitudinally extensive T2-hyperintense intramedullary lesions from T6 to the conus. CSF analysis showed lymphocytic pleocytosis and elevated protein; autoimmune serology confirmed active systemic lupus erythematosus (SLE). SLE-associated longitudinally extensive transverse myelitis (LETM) was diagnosed following exclusion of other differential diagnoses. TREATMENT: High-dose intravenous methylprednisolone, intravenous immunoglobulin (IVIg), and rituximab were administered. Corticosteroids precipitated psychosis, managed with antipsychotics. Maintenance therapy with mycophenolate mofetil and hydroxychloroquine was continued. Despite aggressive immunotherapy, there was no neurological recovery, and the patient remained paraplegic with neurogenic bowel and bladder dysfunction. DISCUSSION: This case underscores LETM as a rare, aggressive manifestation of SLE that can occur even in patients of European ancestry. Despite prompt multimodal immunotherapy, neurological recovery was absent, reflecting the poor prognosis of extensive cord involvement. Early recognition, exclusion of mimics, and coordinated multidisciplinary care are vital to optimise outcomes and quality of life.