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Narcolepsy-cataplexy syndrome is characterized by excessive, severe sleepiness during the day, sudden loss of muscle tone with emotional lability (cataplexy), sleep paralysis, hypnagogic or hypnopompic hallucinations and weight gain. Although none of the major symptoms is exclusive to narcolepsy, cataplexy is the most specific symptom and is rarely present outside of narcolepsy. For the first time as a clinical picture shaped by a sudden loss of muscle tone in 1877 was reported by Westphal. The onset of narcolepsy with cataplexy is usually during teenage and young adulthood (10-15 ages) and persists throughout the lifetime. We purposed to report a case with narcolepsy diagnosed. A-11-year-old male was brought to our hospital due to drop attacks, which had occurred two-three times in a week since three months, when he was playing. It was learned that the patient had sudden loss of muscle tone with emotional changes such as smiling, while he was playing, and after these attacks he had continued to play again. He was sleeping all day long. His teachers recognised the decreased academic performance. Routine blood biochemistry and hematological investigations were normal. Brain Magnetic Resonance Imaging (MRI) and Electroencephalography (EEG), and electromyogram (EMG) were normal. He was subjected to Multiple Sleep Latency Test (MSLT) resulting in the mean sleep latency of 1 minute with presence of excessive daytime sleepiness and demonstrated the presence of sleep-onset REM periods (SOREMP). Neuropsychological tests were normal. After the reevaluation of the history and physical examination, he was diagnosed as narcolepsy. Methylphenidate 10 mg/day treatment was started and the dose was increased to 20 mg/day after two weeks. After two months of methylphenidate treatment, the symptoms were resolved. Narcolepsy is a syndrome characterized by excessive sleeping. Pathophysiological studies have shown that the disease is caused by the early loss of neurons in the hypothalamus that produce hypocretin, a wakefulness-associated neurotransmitter present in cerebrospinal şuid. The cause of neural loss could be autoimmune since most patients have the HLA DQB1 allele that predisposes individuals to the disorder. Treatment is with stimulant drugs (modafinil or the other stimulants; methylphenidate etc.,) to suppress daytime sleepiness, antidepressants for cataplexy, and hydroxybutyrate for both symptoms. A clinical examination and exhaustive medical history are essential for diagnosis and treatment. Narcolepsy is not rare, but it is an underrecognized and underdiagnosed condition at younger age. If left undiagnosed and untreated, early onset narcolepsy can interfere with psychological, social, and cognitive functioning and development andundermine academic and social activities.