What disorder occurs when mechanisms that paralyze the body during REM sleep fail to function?

The disorder that occurs when the mechanisms that paralyze the body during REM sleep fail to function is REM sleep behavior disorder. This disorder is characterized by the individual acting out their dreams because the usual muscle atonia (temporary paralysis) that occurs during REM sleep is absent. As a result, these individuals may physically engage in their dreams, leading to potentially dangerous behavior, both for themselves and for others nearby.

In contrast, narcolepsy involves excessive daytime sleepiness and sudden sleep attacks, but it is not specifically related to the failure of REM paralysis mechanisms. Sleep apnea is characterized by interrupted breathing during sleep and does not involve the acting out of dreams. Restless leg syndrome is marked by uncomfortable sensations in the legs and an irresistible urge to move them, particularly during periods of rest or inactivity, which is also unrelated to the phenomena observed in REM sleep behavior disorder.