Missing the diagnosis in a young woman with repeated hospital admissions: a case report Kleine-Levin syndrome (KLS) is a rare sleep disorder characterized by various symptoms, such as recurrent episodes of hypersomnia, cognitive abnormalities, psychiatric symptoms, hyperphagia, and behavioral disturbances, and is often confused with other diseases. To date, a number of classic cases of KLS have been identified worldwide; however, incomplete forms of KLS without hyperphagia have rarely been reported. Here, we report a case of a repeatedly hospitalized 24-year-old woman who suffered from psychiatric symptoms, abnormal behaviors, cognitive abnormalities, and recurrent episodes of hypersomnia for eight years. During this period, she was admitted three times, and different diagnoses were considered because the symptoms differed each time. In view of the recurrent episodes of hypersomnia, we monitored the patient using polysomnography (PSG). Carbamazepine and methylphenidate extended-release tablets were used to treat the patient, and beneficial effects were observed. Therefore, when a patient presents with recurrent episodes of hypersomnia, particularly those lasting approximately 20 hours per day, we suggest that psychiatrists should the possibility of KLS.