Correlation between the atypical presentation of myasthenia gravis and radio-pathological classification of the thymus – a retrospective cohort study

Myasthenia gravis (MG) is a disease of neuromuscular junction and mainly autoimmune in aetiology. The state of thymus is a critical determinant for the prognosis. In this retrospective review study, we aimed at clarifying the relationship between the mode of clinical presentation of MG and the radiopathological classification of the thymus. We identified patients with MG from the database of our medical center from 1988 – 2017. The patients were classified into two groups according to their clinical presentation: those with a typical presentation with diurnal variation, and those with an atypical presentation of persistent weakness or respiratory failure from the beginning. The underlying thymic state was categorized into six groups: normal, abnormal by imaging (if no operation was performed), hyperplasia, benign thymoma, cortical type thymoma, and malignant thymoma. In total, 227 patients (133 females and 94 males) were included in the analysis, of whom 68% were classified into the typical presentation group. The atypical presentation correlated significantly with thymic categories (p = 0.014) and sex (p = 0.026) but not age at onset (p = 0.232). The atypical presentation was more common in the male patients and in those with thymic carcinoma.