Adult Ocular Myasthenia Gravis Conversion: A Single-Center Retrospective Analysis in China

Abstract

Introduction: The conversion rate from ocular myasthenia gravis (OMG) to generalized myasthenia gravis (GMG) was reported to be much lower in Asian population since most OMG patients are juvenile onset. However, the exact conversion rate for adult-onset OMG to GMG is still unknown. Objective: We aimed to delineate the conversion rate and risk factors for adult patients with ocular onset to GMG. Methods: Adult myasthenia gravis (MG) patients with ocular onset (age > 18 years) were retrospectively reviewed. Patients with confined ocular involvement lasting more than 2 years (pure OMG group) and those who converted into GMG (converted OMG group) were enrolled for subsequent analysis. We then analyzed 5 clinical variables, including onset age, sex, onset symptoms, anti-acetylcholine receptor antibody (AChR Ab), and thymus CT. Survival analysis was applied to all enrolled patients to explore risk factors associated with conversion. Results: In a total number of 249 ocular-onset MG patients initially enrolled, we excluded 122 patients with OMG lasting less than 2 years. The remaining 127 patients were enrolled, including 106 converted OMG and 21 pure OMG patients. Converted OMG patients had an older onset age (threshold: 43 years) and higher anti-AChR Ab titer (threshold: 6.13 nmol/L). The estimated conversion rate was 70.64%. Moreover, 67% of conversion occurred within 2 years after onset. Cox regression of survival analysis revealed that higher anti-AChR Ab titer and bilateral ptosis were associated with a higher conversion rate. Conclusions: The conversion of adult OMG was associated with anti-AChR Ab titer, onset age, and bilateral ptosis. The estimated conversion rate of Chinese adult OMG patients was 70%.

Risk Factors for Generalization in Patients with Ocular Myasthenia Gravis: A Multicenter Retrospective Cohort Study

“…Our study found that patients with adult-onset OMG were more likely to develop generalization than those with the juvenile-onset form of this disease; moreover, those with late-onset OMG had a higher risk of generalization. This finding is consistent with results from previous studies [ 8 , 13 , 14 , 20 , 21 ]. Wang et al reported the group with secondary generalization in their study comprised more late-onset patients [ 8 ].…”

“…Our study found that patients with adultonset OMG were more likely to develop generalization than those with the juvenile-onset [13]. The reported incidence and prevalence of late-onset MG (age of onset C 50 years) have steadily increased over the last decades [22].…”

“…Wang et al reported the group with secondary generalization in their study comprised more late-onset patients [ 8 ]. Feng et al also found converted OMG patients had an older onset age (threshold: 43 years) [ 13 ]. The reported incidence and prevalence of late-onset MG (age of onset ≥ 50 years) have steadily increased over the last decades [ 22 ].…”

“…Seropositivity for AChR-Ab as a predictor of generalization is well-documented [ 5 , 7 , 9 – 11 , 13 , 20 , 28 – 30 ]. Galassi et al surveyed a cohort of 175 patients with OMG and compared the outcome of those patients with antibodies to AChR or to MuSK (muscle-specific tyrosine kinase) with those seronegative for both of these antibodies.…”

“…Several retrospective studies have reported risk factors associated with generalization, however, these studies included patients on immunosuppression therapy or those undergoing thymectomy, which may reduce the generalization risk [2,[5][6][7][8][9][10][11][12][13][14]. Thus, a study exploring risk factors in non-immunosuppressed and nonthymectomized patients is required to adequately control for these confounding factors.…”