As one who has a son who suffers from bipolar disorder and a granddaughter who suffers from mood disorder, NPD, even though not exactly the same as the above, nevertheless does share many of the symptoms, and these fit Trump to a "T".
But notice I use the term "disorder', because it is not something easily controlled. I asked my 44 year old son if he felt that, based on what he has, could ever see himself as president, and he absolutely not. He's too "flighty", if you know what I mean by that, and he knows it.
It makes me wonder if this is why Ivanka is going to stay in the White House as she may have a soothing effect on him, much like my son's wife has that kind of effect on my son.