I've had a few misdiagnoses over the decades. I've also had more doctors and discussions with doctors than I ever wanted to.

Sometimes we forget, or aren't aware, that a medical diagnosis is an educated best guess - an interpretation - based on evidence (symptoms, tests) knowledge, and experience. This also means that a misdiagnosis may not be a mistake; the doctor(s) may have done everything correctly with no reasonable way of knowing that their interpretation was incorrect. It's also possible that they just know more/better now than they did then. Some say that's why medicine is called a "practice". It's certainly why it's sometimes prudent to get a second (or third, etc.) opinion.

http://en.wikipedia.org/wiki/Medical_diagnosis

I'm a believer in the Japanese business adage, "Fix the problem - not the blame". It's never been productive for me to dwell too much on those misdiagnoses, but to deal with what things are and proceed accordingly.

Doc