Outcomes of Treatment in Ocular Myasthenia Gravis Based on Minimal Manifestation: A Real-World Retrospective Cohort Study

Abstract

Background: Myasthenia gravis (MG) is a chronic autoimmune disorder characterized by muscle weakness caused by autoantibodies targeting acetylcholine receptors. Prednisolones improve symptoms by reducing autoantibody activity, but its optimal use, particularly in ocular myasthenia gravis (OMG), remains unclear due to limited trials and variable responses. Objective: To evaluate the clinical efficacy, optimal dosing, and predictors of first minimal manifestation (MM) with oral prednisolone in myasthenia gravis, based on the Myasthenia Gravis Foundation of America Post-Intervention Status (MGFA-PIS). Methods: Patients with OMG treated with oral prednisolones between 1st January 2015 and 31st December 2022 at Rajavithi Hospital were retrospectively reviewed. Baseline data, dosing, efficacy, and outcomes were analyzed using Cox regression and survival curves to identify predictors and time to first MM. Results: Of the 101 OMG, 81 patients (80.2%) achieved MM. The mean age was 46.6 ±6.9 years in the MM group and 46.2 ± 6.0 years in the non-MM group. The mean daily dose of pyridostigmine was significant higher in the MM group (152.68 ± 32.38 mg/day) compared to the non-MM group (133 ± 34.50 mg/day) (p = 0.018). The prednisolone dosage was comparable between the two groups. Seropositivity of AChRAb, thymoma, thymectomy, concurrent autoimmune diseases were notably observed in non-MM group (p < 0.05, respectively). Cox proportional hazards analysis and survival curves revealed higher pyridostigmine dosage (HR 1.713, 95% CI: 1.029–2.849, p = 0.038). Prednisolone initiation at 6–12 months reduced MM (HR 0.527, 95% CI: 0.297–0.936, p = 0.029), with further reduction observed beyond 12 months (HR 0.165, 95% CI: 0.073–0.368, p < 0.001). The presence of AChRAb, thymoma, prednisolones dosage and ophthalmic manifestations demonstrated no significant association with the achievement of minimal manifestation. Conclusion: Early prednisolone initiation (within 6 months) and higher pyridostigmine doses were linked to remission, highlighting treatment factors over demographics in OMG outcomes.