ObjectiveTo explore the risk factors of myasthenic crisis after thymectomy (MCAT) for patients with myasthenia gravis (MG). MethodsWe searched PubMed, EMbase, The Cochrane Library (Issue 8, 2015), Web of Knowledge, CBM, CNKI and WanFang Data from inception to August 31, 2015, to collect case-control studies and retrospective cohort studies about the MCAT for patients with MG. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then meta-analysis was performed using Stata 13.0 software. ResultsA total of 17 studies involving 394 patients with myasthenic crisis and 1642 controls were included. Of the 17 studies, 11 were retrospective cohort studies and 6 were case-control studies. The results of meta-analysis showed that:a) univariate analysis indicated that history of myasthenic crisis (OR=8.05, 95%CI 5.80 to 11.15, P<0.01), bulbar symptoms (OR=5.10, 95%CI 3.01 to 8.67, P<0.01), preoperative severity of gravis (Osserman-stage) (OR=10.55, 95%CI 7.28 to 15.30, P<0.01), postoperative pulmonary infection (OR=10.77, 95%CI 3.88 to 29.95, P<0.01), thymoma (OR=2.37, 95%CI 1.50 to 3.75, P<0.01), dose of pyridostigmine (MD=0.45, 95%CI 0.29 to 0.62, P<0.01), AChRAb level >100 nmol/L (OR=12.14, 95%CI 4.80 to 30.73, P<0.01) and operation time (MD=0.57, 95%CI 0.26 to 0.88, P<0.01) were the risk factors of MCAT; b) multivariate analysis showed that, history of myasthenic crisis (OR=5.06, 95%CI 2.30 to 11.14, P<0.01), bulbar symptoms (OR=5.21, 95%CI 2.62 to 10.35, P<0.01), preoperative severity of gravis (Osserman-stage) (OR=5.82, 95%CI 2.60 to 13.04, P<0.01) and AChRAb level >100 nmol/L (OR=8.38, 95%CI 3.31 to 23.08, P<0.01) were the independent risk factors of MCAT. ConclusionThe independent risk factors of MCAT for patients with MG are history of myasthenic crisis, bulbar symptoms, preoperative severity of gravis (Osserman-stage) and AChRAb level >100 nmol/L.