According to the Mayo Clinic and a couple other websites, these are some of the symptoms of Narcissistic Personality Disorder:
1. If you have Narcissistic Personality Disorder, you may come off as conceited, boastful, or pretentious. You often monopolize conversations. You may feel a sense of entitlement.
2. You also have trouble handling anything that may be perceived as criticism. You may have secret feelings of insecurity, shame, vulnerability and humiliation. To feel better you may react with rage or contempt and try to belittle the other person to make yourself appear superior.
3. Having an exaggerated sense of self-importance.
4. Expecting special favors and unquestioning compliance with your expectations.
5. Having an inability or unwillingness to recognize the needs and feelings of others around you.
6. Behaving in an arrogant or haughty manner.
7. Cannot admit fault or accept blame for anything.
8. When having NPD you may not want to think that anything is wrong because doing so wouldn't fit in with your self-image of perfection. But there are treatments available. Consult your physician.
This is only a sample of what was listed. Just throwing this out there in hopes that it could help other people who suffer from knowing someone with this debilitating mental disorder.