Anxiety Disorders -- and especially Generalised Anxiety Disorder (GAD) -- are often misdiagnosed as Narcissistic Personality Disorder (NPD).

Anxiety is uncontrollable and excessive apprehension. Anxiety disorders usually come replete with obsessive thoughts, compulsive and ritualistic acts, restlessness, fatigue, irritability, difficulty concentrating, and somatic manifestations (such as an increased heart rate, sweating, or, in Panic Attacks, chest pains). (From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 2 DVDs with 12 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)