Kleine-Levin syndrome (KLS) is a rare disease characterized by recurrent episodes of hypersomnia, hyperphagia and behavioural symptoms, mainly hypersexuality.

We report the clinical course of KLS in a 18-year-old male. The clinical onset and evolution are described.

The boy was diagnosed as having KLS after two episodes of hypersomnia lasting for 13 to 15 days each one. When awake, he was depressed and with megaphagia. He also had phases of hypersexuality. The initial interval between episodes was 6 weeks. After the second episode was treated with lithium and remained free of symptoms for 11 months. He had a third episode that lasted 6 days. Serum lithium level was low. In this third episode he had only hypersomnia. He had a relapse two years later with a duration of 4 days, without further relapses.

KLS is more frequent in young males with a mean duration of 8 years and around 7 episodes that lasted 10 days. The pathogenesis remains unknown. It has been related with functional disturbance in the hypothalamus, viral infections, triggering stimulus...Some authors consider KLS as a variant of bipolar disorder. Treatment includes methylphenidate, neuroleptics, antidepressants and mood stabilizers as lithium. With lithium has been reported fewer relapses, shorter duration of episodes and disappearance of behavioural symptoms.

Despite being a rare disease, is thought to be underdiagnosed, because diagnosis is mainly clinical, and tests such as EEG, PSG and MSLT reinforce the diagnosis but are not pathognomonic. Today, lithium is the best treatment option.