RESUMO
INTRODUCTION: In myasthenia gravis (MG) patients on intravenous methylprednisolone (IVMP) therapy, initial deterioration should be carefully monitored because it may cause myasthenic crisis. The aim of this study was to investigate the onset, duration and related factors of initial deterioration from the first IVMP in MG patients. METHODS: A total dose of IVMP in the first cycle of 750 mg or less, over 750 to 1500 mg, and over 1500 to 3000 mg was used in the analysis. Initial deterioration was evaluated in qualitative and quantitative evaluation and was defined as an increase of 2 or more points on the The Myasthenia Gravis Activities of Daily Living (MG-ADL) scale after the start of IVMP therapy in the quantitative evaluation. RESULTS: We enrolled 51 mainly mild MG patients. The mode of onset of initial deterioration from the first IVMP treatment was day 4 in the qualitative and quantitative evaluation. In addition, the mode of duration was 3 days. In multiple logistic regression analysis, factors related to initial deterioration were MGFA classification with overall disease duration up to just before IVMP and thymectomy before IVMP in both the qualitative and the quantitative evaluation (p < .001). One to four cycles of IVMP improved the MG-ADL score at hospital discharge from that at the start of IVMP (p < .001). CONCLUSION: Disease severity and thymectomy before IVMP are related to initial deterioration in MG patients. IVMP can be repeated after initial deterioration weekly in most patients.