The symptoms vary from one personality disorder to another. Personality disorders are the most difficult disorders to treat. The people who have them, in many cases, do not seek help because they are able to live normally in some ways - keeping a job, for example. It is in the area of relationships with other people that they run into trouble. They tend to blame others rather than consider that the problem is within themselves.
Treatment consists of intensive psychotherapy, sometimes supplemented with medication.
They are the result of physical disease or injury to the brain. Treatment usually consists of rehabilitation programs. Some people think that describing mental illness according to diagnosis causes stigma by labelling people. However, if you want to do some research, you'll need to know what your illness is called. A person is not an illness.