KLS is a rare disorder characterised by recurrent episodes of excessive sleep, associated with reduced understanding and altered behaviour. KLS usually starts in the teenage years, but can occur in younger children and adults.

Each episode can last days, weeks or months. Individuals in episode are often not able to care for themselves, attend school or go to work. Between episodes they go back to being themselves with normal sleep, understanding and behaviour.

It can be difficult to diagnose and treat but the impact on young people and their families is devastating.