Very late-onset multiple sclerosis: Diagnostic and therapeutic challenges: Case report

Background Multiple sclerosis (MS) is the most common inflammatory autoimmune disease of the central nervous system and predominantly affects young adults, with peak onset between 20 and 40 years of age. However, in rare cases, the disease may occur after the age of 50, referred to as late-onset multiple sclerosis (LOMS), which can pose significant diagnostic and therapeutic challenges. Case Presentation A 75-year-old woman presented with diplopia and hemiparesis with an Expanded Disability Status Scale (EDSS) score of 6. Her medical history included idiopathic cardiomyopathy and watermelon stomach. Over the preceding two years, she had experienced two previous neurological episodes presenting as left hemiparesis and left lower limb weakness. These episodes were initially misdiagnosed as ischemic stroke, and, later, metastatic malignancy was suspected. Brain and cervical magnetic resonance imaging revealed multiple white matter lesions in typical demyelinating locations as well as a cervical spinal cord plaque, with contrast enhancement in several lesions. After exclusion of alternative diagnoses, the patient was diagnosed with very late-onset relapsing–remitting multiple sclerosis (RRMS). Treatment with intravenous methylprednisolone (IVMP) resulted in improvement of the EDSS score from 6 to 3/5. Due to recurrent attacks and severe gastrointestinal bleeding associated with corticosteroid therapy, high-efficacy disease-modifying therapy was initiated with natalizumab. Fifteen months later, treatment was switched to rituximab following the detection of JC virus seropositivity. Subsequently, after 18 months, there was a DMT de-escalation to teriflunomide. Currently, after 43 months of follow-up, the patient remains both clinically and radiologically stable. Conclusion This case highlights the diagnostic complexity of very late-onset MS, which may initially mimic more common conditions such as cerebrovascular disease or malignancy. Early recognition and individualized therapeutic strategies are essential to prevent disability in elderly patients.