The proverb: "No good deed goes unpunished" is a good introduction to understanding the much misunderstood condition known as borderline personality disorder. Any personality disorder is a fixed, lasting pattern of thinking, feeling and acting that usually leads the person into emotionally and/or physically dangerous situations.

I've been treating a 43-year-old woman for 20 years. Because of our long-term history, one would think that she would know and trust me. However, the complexity of BPD became very clear when I volunteered to go with her to help her interpret the results after her uterine cancer was removed. She was scheduled to get a follow-up visit with her ob-gyn doctor, but she was so terrified of what she'd hear that she couldn't bring herself to go. I was in the hospital that day so I offered to stop by during her visit and help my patient deal with whatever results she obtained. She said she was grateful and would go if I were present.

That day I went into the ob-gyn's office with her and sat across from the doctor who reported great news that the patient was cancer-free. I nodded happily and felt good for her and the positive results. Out in the hallway, out of the other doctor's hearing range, my patient yelled and cried.

"You colluded with her! I can't believe how you doctors were so self-satisfied. You didn't even consider me. You and that doctor talked down to me like I was a moron!"

"But you're cancer-free! You're okay. Aren't you happy about that?" I was so surprised by her reaction I could hardly think or speak. Then I realized that she hadn't even registered the positive news. She had been waiting for something negative and that was all she could hear or see.

"I hate you both!" she screamed and ran down the hall. I dashed after her, calling her name, but she jumped into an elevator and ran off.

Later that evening she called me to apologize and thank me for going with her. The good news had finally sunk in. Her reactions are indicative of how severely she suffers from borderline personality disorder and how difficult it is for her to process information and have healthy interpersonal relationships.

People with borderline personality disorder have incredible challenges when dealing with others and themselves because they have inflexible negative behavior patterns, an unstable self-image, uncontrollable emotions, and impulsivity. Their condition is due to a combination of genes, a childhood environment of abuse, turbulence and/or neglect, and erratic biochemistry.

You may be encountering a person with borderline personality disorder if you confront this type of behavior:

1) You are idealized sometimes as the greatest person alive, while at other times you are seen as the worst person. People with BPD often have skewed views of people, whether they be acquaintances or people that are an everyday part of their lives.

2) The person's sense of self is distorted. The person doesn't truly understand who he or she really is, so he or she tries on different behaviors. It is not uncommon for them to be distant, authoritative, friendly or hostile with the same person in the same day.

3) The person frantically tries to avoid what she considers abandonment. The person may act overly needy when their support system is removed, even temporarily, such as when a close friend goes on vacation.

4) The person tries to kill him -- or herself or engages in self-mutilation. If you witness this behavior in anyone, immediately call 911.

5) The person is intensely reactive to situations or events that most people would just ignore or brush off. My patient's reaction to the positive news about her cancer is a good example. Another example is the way a person with BPD might obsess about a situation or statement. If someone tells this individual something in an angry way, then he or she might keep thinking about the statement obsessively and cannot "let it go."

6) He or she constantly feels empty or not really there. My patient reported these feelings of emptiness many times and often thought she wasn't really in this world.

7) Anger is their most common emotion even when other feelings might be more appropriate. For example, when a person with BPD learns he/she has won a game in tennis, he or she might rant about the opponent instead of just enjoying the victory.

8) Paranoid thoughts are common. People with this disorder often become paranoid and imagine that people are "colluding" against them.]

9) These people act impulsively and in self-damaging ways, for example, engaging in compulsive sex, binge-eating or gambling. Because of this, BPD can often be confused with other personality disorders, such as histrionic personality disorder.

If you think a friend, co-worker or family member might be suffering from borderline personality disorder, encourage him or her to seek treatment. Sometimes, it's best to avoid personal contact or deal with the person only in a group setting, such as the workplace or group outings. The most important tool is not to internalize the person's behavior, or take it too personally. Remember it's not about you. People with borderline personality disorder aren't fully aware of their behavior and the effect on other people. Try to be as sympathetic as you can, but maintain appropriate boundaries to protect yourself.