Narcolepsy

Overview

associated with HLA-DR2
it is associated with low levels of orexin (hypocretin), a protein which is responsible for controlling appetite and sleep patterns
early onset of REM sleep

Features

typical onset in teenage years
hypersomnolence
cataplexy (sudden loss of muscle tone often triggered by emotion)
sleep paralysis
vivid hallucinations on going to sleep or waking up

Investigation

multiple sleep latency EEG