Association of Smoking and Generalized Manifestations of Myasthenia Gravis

OBJECTIVE: Smoking is a known risk factor for the development and progression of autoimmune diseases. Previous studies in ocular myasthenia gravis (MG) patients showed that smoking is associated with the severity of symptoms and progression to generalized MG. However, whether smoking affects MG symptoms in patients with a broader clinical spectrum of presentations is unknown. Therefore, in this study, the associations of smoking with the clinical characteristics of MG were analyzed in a cohort of patients including those with generalized, seronegative, and thymoma-associated MG. METHODS: The smoking history was investigated in a cross-sectional study of 187 patients with MG followed in a referral hospital for neurology. The association of smoking with MG-activities of daily living score at survey, the presence of generalized manifestations, and the age of onset was assessed using multiple regression models. RESULTS: Neither current nor prior smoking habit was associated with the MG-activities of daily living score at survey. However, smoking exposure after MG onset was significantly associated with the presence of generalized manifestations during the disease course (odds ratio, 3.57; 95% confidence interval, 1.04, 12.3). The smoking history before or at onset of MG was not associated with the age of onset. CONCLUSION: Smoking exposure after the onset is associated with generalized manifestations of MG in our cohort of patients with a broad clinical spectrum of presentations.