AIM:To understand the distinct,clinical features of myotonia congenita in China.METHODS:Case reports of myotonia congenita were retrieved from the Chinese Journal Full-text database,dating between 1980 and 2007,and analyzed for clinical characteristics of myotonia congenita. RESULTS:There were 35 published reports and 258 cases about myotonia congenita.Six reports(62 cases)were excluded due to lack of clinical data,imprecise diagnosis,or duplication.Finally,29 published reports and 196 cases(140 males and 56 females)were included in this analysis.About 78.6% of patients were diagnosed with myotonia congenita before the age of 20,and among these, 86.1% were classified as dominant inheritance.Lower and upper extremities were frequently affected with severe symptoms.Eyelids,mouth and lingual muscles,and trunk muscles and cervical muscles were less frequently involved.However,muscles for swallowing,sphincter muscles,and smoothmuscles were not involved.There were no reports of cataracts,cardiac conduction block,or dyscrinism. Myotonia congenita symptoms were induced or aggravated by cold temperatures in 71.9% of the patients and warming-up effect occurred in 95.6% of the patients.Muscle hypertrophy was observed in 69.6% and percussion of muscles in 76.5% of the patients.Myotonia potential or myotonia-likepotential was detected in all patients using electromyography.Muscle fiber swelling or hypertrophy was frequently detected through muscular biopsy.CONCLUSION:Myotonia congenita frequently occurs in males before the age of 20,in particular as the autosomal dominant form of myotonia congenita.Skeletal muscles throughout the body,especially the lower and upper extremities,are involved.However,muscles for swallowing,sphincter muscles, and smooth muscles are not involved.Warming-up effect is the main characteristic of myotonia congenita.