Parenchymal Neuro-Behçet's disease or Comorbid Behçet's disease with multiple sclerosis: A discriminative analysis of a complex clinical entity

Background: Patients with Behçet's disease (BD) may rarely manifest with cerebral white matter lesions resembling multiple sclerosis (MS). This may result in misdiagnosis due to diagnostic difficulties between parenchymal neuro-BD (pNBD) and MS. This study aims to elucidate the distinguishing features of patients with comorbid BD and MS (BD+MS) in comparison to those with pNBD and MS alone by focusing on clinical and laboratory features. We also aimed to identify the distinctive characteristics of BD+MS patients by comparing them to patients with pNBD and MS.

Methods: The methodology of this study involved a retrospective analysis of patient records followed in the Department of Neurology at the Istanbul Faculty of Medicine, Istanbul University. The study population included patients diagnosed with pNBD, MS, and a comorbid condition of BD and MS (BD+MS). We assessed clinical, radiological, and laboratory data, including disease onset, annual relapse rates, Expanded Disability Status Scale (EDSS) progression, and cerebrospinal fluid examination. Several parameters were examined between the pNBD, MS, and BD+MS patient groups to find similarities and differences between subgroups.

Results: Our study included 1,764 patients: 172 with pNBD, 1,574 with MS, and 18 with BD+MS. A predominance of females was noted in the BD+MS (72%, p < 0.001) and MS (69 %, p < 0.001) groups compared to pNBD (30 %). The median age at the onset of neurological symptoms was 35.5 (IQR: 16.8) years for BD+MS, 34.6 (13.6) years for pNBD, and 27.6 (13.3) years for MS (BD+MS vs. MS; p = 0.3, pNBD vs. MS, p = 0.7). Additionally, the number of attacks was notably different, with BD+MS patients experiencing a median of 3.5 (2.0) attacks compared to 3.0 (3.0) for MS patients and only 1.0 (1.0) for pNBD patients, suggesting a more active disease course in the MS and BD+MS groups compared to pNBD (p < 0.001). The median annualized relapse rate for BD+MS was 0.3 (0.2), which was lower than the rate of 0.4 (0.4) in MS (p = 0.048) and equivalent to the rate of 0.2 (0.3) in pNBD (p = 0.2). The time to the first relapse was similar to those with BD+MS and MS, but considerably shorter than in individuals with pNBD (p < 0.0001). The cerebrospinal fluid (CSF) analysis showed no significant differences in neutrophil and lymphocyte counts between BD+MS and MS patients but elevated levels in pNBD patients (p < 0.05). CSF protein levels were consistent across all groups (p = 0.1 and p = 0.7). Oligoclonal bands were detected in all patients with BD+MS, in the majority of MS patients (83.6 %), and a small percentage of pNBD patients (19.7 %), showing a notable distinction between the BD+MS and pNBD groups (p < 0.001).

Conclusion: Our study underscores the need for a skeptical approach in diagnosing and treating patients with BD who exhibit symptomatic MS-like MRI lesions. Our findings suggest that BD+MS is a distinct clinical entity, warranting specific diagnostic and treatment approaches. Our findings highlight that BD patients with MS-like lesions meeting MS diagnostic criteria should be managed as patients with comorbid MS and BD rather than pNBD.