Dissociative disorders result from a dissociation so severe that usual integration of consciousness and perception of self break down. It can come on suddenly or gradually, and can be transient or chronic.
Understandably, symptoms cause distress or impaired functioning.
Amnesia is the inability to recall important personal information, usually of a traumatic or stressful nature. Amnesia can be localized, selective, or generalized.
Fugue is the sudden, unexpected travel away from home or workplace, with the inability to recall some or all of one's past; a new identity may be taken.
Identitiy disorder, aka multiple personality disorder, is the rpesence of two or more distinct personalities who take control of an individual's behaviour.