As Sigmund Freud’s theories regarding personality and the subconscious mind took root and became a field unto itself, other scholars and scientists sought to build upon his work. One of the areas on which there was much focus involved “narcissism,” or an extreme level of self-absorption and an exaggerated sense of self-importance, combined with an absence of empathy for the suffering of others. From the study of narcissism as a form of personality disorder, Heinz Kohut, an Austrian-born (as was Freud, the father of psychoanalysis) American psychoanalyst developed the theory of narcissistic personality disorder that includes on its spectrum of reaction to real or perceived slights the concept of “narcissistic rage.” Narcissistic rage is an extreme, sometimes violent reaction to such slights, in which the narcissistic personality responds to a perceived “injury” by verbally or physically lashing out at the “attacker.” The “attack,” to reiterate, is not physical, and may not even be real, but is perceived by the narcissistic individual as a very real attack on his or her self-esteem.
This is a reaction to narcissistic injury, this is a "perceived threat to a narcissist's self-worth" which in many times is their ego. This can be differentiated between regular rage and narcissistic rage because in narcissistic rage, it can occur if someone's desires are left unmet, with their reaction to be a childish one, not thinking with their heads and never growing from their faults.
Narcissistic rage is due to a response of narcissistic injury. Narcissistic injury is when there is," a perceived threat to a narcissist's self-esteem or self-worth." Narcissistic rage can either be very extreme where it becomes violent and explosive or passive-aggressive where the narcissist withdraws from someone and essentially gives them the "silent treatment."
Narcissistic rage can be triggered by things that would normally make someone just angry. This is how to tell the difference between it being anger or an actual rage. This rage normally occurs due to problems growing up during the developmental stages of life where certain important needs were unmet. This causes problems in emotional development and causes severe rage because the narcissistic never was able to get past the immature rage. They never grew from it to learn how to control it and react to certain situations with just anger. Instead they resort to child-like tendencies and therefore rage. Rage is one step above anger and the highest level of anger to get to.