Personality Disorders may be defined as ingrained habits, or patterns of behavior, that are recognized at an early age. Individuals suffering from these diseases are unable to adapt to new situations as a result of these rigid patterns of behavior.
Eventually, this mode of behavior lead the individual to act in a self-centered and destructive fashion.
The worrying fact is that these individuals perceive their behavior as normal. They do not believe they are ill.
This video lists the 10 common types of personality disorders, and their signs and symptoms.