Ocular manifestation and generalization after ocular onset in ocular myasthenia gravis: A 5-year analysis

Parinee Kemchoknatee,¹ Apisama Arepagorn,² Thansit Srisombut²

¹ Department of Ophthalmology, Rajavithi Hospital, Bangkok, Thailand
² Faculty of Medicine Rajavithi Hospital, Rangsit University, Bangkok, Thailand

Abstract

Background: Ocular Myasthenia Gravis (OMG) is an autoimmune disease which causes ptosis, diplopia, or both. There is very limited information on the presenting symptoms, treatment trends, factors influencing generalization, and treatment outcome in Thai populations.
Objective: To investigate characteristics of the presenting symptoms, associated factors for conversion to Generalized-MG (GMG), and treatment outcome in OMG patients.
Methods: We analyzed data from patients diagnosed with OMG between January 2015 and December 2020 at Rajavithi Hospital, Thailand. We investigated disease generalization in time-to-event analysis and compared factors associated with disease generalization using a Cox-proportional-hazards model.
Results: Of the 155 consecutive patients, 106 (68.4%) were female and their mean (SD) age was 49.3 years (15.51). There were 123 (79.35%) and 32 (20.6%) patients in the remained OMG and GMG groups respectively. Ptosis was the presenting symptom in 147 (94.8%) patients, diplopia alone was found in 8 (5.2%), and both symptoms were present in 53 (34.2%) patients. GMG patients had a higher proportion of combined ptosis and diplopia (p = 0.01), and positive AChR-Antibody test (p = 0.013). Overall, 32 (20.65%) patients converted to GMG, mostly in the first 48 months. Multivariate Cox-proportional-hazard model identified positive AChR-Ab test as a risk factor for generalization (HR, 5.32, 95% CI; 1.02-27.84).
Conclusions: The conversion rate to GMG in our study was 20.65%. The presence of AChR-Ab was identified as a risk factor for generalization of the disease; therefore, patients with OMG should be advised to test for AChR-Ab for both diagnosis and prognosis purpose.
Key word: Ocular Myasthenia Gravis, Generalized Myasthenia Gravis, Ptosis, Diplopia, Autoantibodies/immunology, Receptors, Cholinergic/immunology, AChR antibodies, Acetylcholinesterase inhibitors, Treatment outcome,