INTRODUCTION KLEINE LEVIN SYNDROME (KLS) IS A RARE AND PROBABLY UNDERDIAGNOSED DISORDER. 1,2 The definition of KLS includes the triad of periodic hypersom- nia, hyperphagia, and hypersexuality. Abnormal behaviors are also characteristic. Based on the International Classification of Sleep Disorders, 3 a monosymptomatic form of the syndrome with recurrent hypersomnia appear- ing without binge eating and hypersexuality also exists. Willi Kleine already noted the predilection of the syndrome for males since his first report on five boys with KLS in 1925. 4 Additional affected males were described by Max Levin in 1929, and later in 1936. 5-6 Critchley and Hoffman, who coined the term KLS in 1942, were the first to suggest that the syndrome 7 exclusively affects adolescent boys. Critchley, in 1962, reported on 11 male patients, and then reviewed 15 additional young boys from the literature. 8 Although females with KLS have been encountered, the common belief is that those are exceptional cases. Indeed, descriptions of such cases gained publicity as "females with KLS." The common knowledge that females are the exception to this diagnosis can explain the delay in the diagnosis of girls presenting the typical features of KLS. The purpose of this paper is to describe eight young women with recurrent hypersomnia, of whom four present- ed the classical triad of KLS, and to compare them to age- matched male cases and to reported females from the liter- ature. Patients and Methods During the years 1982–1998 we encountered eight girls with recurrent hypersomnia. In four we were able to per- form nocturnal polysomnographic recordings. The other four either refused to be studied in the sleep laboratory, or could not be sent for recordings due to various technical reasons. In one girl, a recording was performed during a hypersomnolent attack, and in three others, inbetween attacks. All recordings were conducted for one night only. Polysomnographic recordings were performed at the Technion Sleep Laboratory according to standard criteria in 30-second epochs. 9 Recordings included two channels of EEG (Oz-A1 and Cz-O1), EOG, EMG, respiratory effort by a respiratory belt, oro-nasal airflow, and leg movements. Hospital admission and outpatient charts were reviewed and details of the clinical and laboratory work-up were tab- ulated. During the same period, we diagnosed KLS in 26 males: of these, eight males with similar ages to the female patients were selected for comparison purposes. A comput- erized literature search for females with KLS using the key words: "KLS," "Periodic hypersomnolence," and "recur- rent hypersomnia" was performed for the period 1924–1998 using the Medline and PubMed databases, as well as other sources. RESULTS The demographic and clinical data of eight females with KLS are summarized in Table 1. The mean age at onset was 15.1±3.5 years; mean diagnostic delay from the first appearance of the symptoms to the time a KLS diagnosis was made, was 2.56±1.9 years; mean duration of a hyper- somnolent attack was 9.9±5.4 days; and the mean number Abstract: During the years 1982–1998, we encountered 7 adolescents and one young woman suffering from KLS. In 4 patients, hypersomnolence was accompanied by hyperphagia and hypersexuality, while in the remaining 4, recurrent hypersomnia was the only symptom. Mean age at onset of hypersomnolent attacks was 15.1±3.5 yrs. The mean duration of a hypersomnolent attack was 9.9±5.4 days, and the number of attacks per patient was 6.2±3.4. Polysomnographic recordings from 3 patients inbetween attacks, and from one patient during an attack, showed relatively normal sleep structure with decreased sleep efficiency due to numerous awakenings from sleep stage 2. Besides the recurrent hypersomnia, all patients enjoyed good health, with no evidence of behav- ioral or endocrine dysfunction. Similarly aged males with KLS from our clinic and previously reported females, had similar clinical features. A. Kesler, 1 N. Gadoth, 1 G. Vainstein, 1 R. Peled, 2 P. Lavie 2 Department of Neurology, Sapir Medical Center, Meir General Hospital, Kfar Saba, the Sackler Faculty of Medicine, Tel- Aviv University, 1 and The Sleep Laboratory, B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 2 Israel Accepted for publication September 1999 Address correspondence to: Peretz Lavie PhD, Sleep Laboratory, (Faculty of Medicine), Technion —Israel Inst. of Technology, Haifa 32000, ISRAEL. Tel: 972-4-8226730, Fax: 972-4-8323045 Kleine Levin Syndrome (KLS) in Young Females—Kesler et al SLEEP, Vol. 23, No. 4, 2000 1 Kleine Levin Syndrome (KLS) in Young Females KLEINE LEVIN SYNDROME (KLS) IN YOUNG FEMALES