What is the difference between APD and Social Anxiety?

from here: Social Anxiety Disorder and Avoidant Personality Disorder

"Similarity to SAD - Research has found few differences between the kinds of symptoms that people with SAD and APD have. Because of the similarities between SAD and APD, people are often diagnosed as having both disorders. Like SAD, the central fear of people with APD is rejection, ridicule and humiliation by others. However, people with APD tend to have a broader range of symptoms, and the symptoms tend to be more severe"