Pattern of ocular involvement in myasthenia gravis with MuSK antibodies

Background Myasthenia gravis (MG) with antibodies to the muscle-specific kinase (MuSK) has a characteristic phenotype. Ocular manifestations have not been systematically evaluated. Objective To investigate the features of extrinsic ocular muscle involvement in patients with MuSK-MG. Methods We retrospectively evaluated the prevalence, time of onset, clinical pattern and outcome of ocular symptoms in 82 patients with a clinical follow-up ≥2 years. Results Ocular manifestations were observed in 79 patients (96.4%) and were the presenting symptoms in 48 (58.5%). Intermittent diplopia with subtle ophthalmoparesis was the most common complaint, ptosis was generally symmetrical and conjugated gaze paresis occurred in 35% of the patients. Ocular manifestations responded well to prednisone and partially to symptomatic treatment. A few patients developed chronic symmetrical ophthalmoparesis, associated with persistent weakness in other muscle groups. All patients with ocular presentation progressed to generalised disease, though weakness spread to other muscle groups was considerably delayed in a few cases. Conclusions In MG with antibodies to MuSK, ocular manifestations were as frequent as in other disease subtypes. Symmetrical ophthalmoparesis with conjugated gaze limitation was rather common and associated with low functional disability. A proportion of these patients developed chronic eye muscle paresis.