Narcissistic personal disorder is a known pattern of behavior that in most cases they don't have empathy or care for other people's feelings.   They don't come into consideration of there actions or choose to not care for others but more for themselves.  Some ways someone may use NPD in different ways of work is trying to take over a supervision position or tries to take over as they are the boss.  Talking over other and demanding things to be done on a timely ,matter.   In a relationship it can be from controlling what he or she says to others as well what they can and can't do regards answers.  This can affect both in relationship and work a bad environment to live in and for things to get worse mentally and emotionally to the person that is being controlled by someone that is NPD.