What Is Narcissistic Personality Disorder

On one my areas of expertise is Narcissistic Personality Disorder. I think many people can relate to knowing someone with these particular tendencies. To explain what this disorder is, please read the article from PsychCentral:

Narcissistic Personality Disorder is characterized by a long-standing pattern of grandiosity (either in fantasy or actual behavior), an overwhelming need for admiration, and usually a complete lack of empathy toward others. People with this disorder often believe they are of primary importance in everybody’s life or to anyone they meet. While this pattern of behavior may be appropriate for a king in 16th Century England, it is generally considered inappropriate for most ordinary people today.