Aggressive phenotype of multiple sclerosis, characterised by atypical initial symptoms and a fulminant clinical progression.

A previously healthy male in his late 40s presented with progressively worsening neurological symptoms-tetraparesis, visual disturbances, aphasia and dysphagia. Brain MRI revealed multiple large contrast-enhancing lesions with mass effect. After extensive investigation, a demyelinating central nervous system (CNS) disease was suspected; however, a differential diagnosis with primary CNS vasculitis was also considered. Despite treatment with high-dose corticosteroids, plasma exchange and immunoglobulins, the patient's neurological condition continued to deteriorate. A brain biopsy confirmed an active demyelinating process. A diagnosis of aggressive multiple sclerosis was established. Immunotherapy with ocrelizumab resulted in clinical stabilisation. This case highlights the diagnostic challenges of atypical demyelinating presentations and the critical role of brain biopsy in guiding early treatment in fulminant cases.