Confusion in Diagnosis: NMOSD Patients Mistakenly Treated for Multiple Sclerosis

Introduction - Neuromyelitis optica spectrum disorders (NMOSD) and multiple sclerosis are inflammatory immune-mediated diseases of the central nervous system with relapsing attacks of neurological signs related to involvement of multiple functional systems. However, they have distinct treatment, and alarmingly, many drugs effective for MS can exacerbate NMOSD, highlighting the importance of accurate diagnosis. Objectives - To assess the frequency of misdiagnosis and inappropriate treatment of NMOSD as MS. Methods - We conducted a retrospective analysis of medical records from a cohort of NMOSD patients consecutively evaluated at our MS Center, all meeting the 2015 IPND criteria. We assessed demographic and clinical data, with a focus on patients previously diagnosed with MS and treated with MS-specific therapies. Results – The study included 85 patients, 15 (17.6%) having been previously treated for MS. Among these cases, the majority were female (86.7%), 8 (53.3%) were white, and 7 (46.7%) were of mixed race. The mean age at NMOSD onset was 28.2 years (range: 5-55 years). Aquaporin-4 antibodies (AQP4-IgG) tested positive in 8 (53.3%) patients and negative in 6 (40%). One patient (6.7%) lacked data on AQP4-IgG serum status. The average EDSS score at the last evaluation was 4.96 (range: 0-8.0), and the mean disease duration was 110.9 months (range: 42-264 months). Conclusion - The symptoms of NMOSD can mimic those of MS, leading to potential misdiagnosis, which poses significant risks to patients with NMOSD. Misdiagnosing NMOSD as MS can result in inappropriate treatment with disease-modifying drugs which can exacerbate NMOSD symptoms and potentially lead to severe relapses or disability progression in NMOSD patients. Our findings underscore the urgent need for increased awareness and education among clinicians.