Tracy,

One of the problems is that biological systems are much more complex than our understanding. This is why there is still place for research and finding more answers to numerous questions.

With the growing knowledge and understanding of biological systems there have been numerous paradigm shifts and it is naive to think that there are not going to be many more in years to come.

I once read an excellent historical review regarding myasthenia gravis. What amazed me most was the following paragraph:

Despite this understanding of the limitations (and also strengths) of science and medicine, he goes on as if we are now at the time of ultimate enlightenment in the understanding of MG.

This was written in 2003, there is no mentioning of MuSK, there is no mentioning of possible mechanisms leading to myasthenia which are not due to abnormalities of the AchR itself. (Despite growing evidence, this is suprisingly still controversial in the MG community and the SFEMG is still seen as the gold standard by many). There is very little mention of open questions in the understanding and management of MG.

In fact he writes that

Obviously, this is correct if you take out all those patients with normal tests that don't fit the accepted paradigm of MG, all those patients who continue to have myasthenic-like symptoms of fatigue despite being in full remission, all those patients who fail to respond to effective treatments because they are not "positive" enough.

This near-sited view of a leading expert in the field of myasthenia-A very smart and knowledgeable physician, is the best example for why this approach is so problematic.

How can you rule out a disease which has not been described yet?

For instance, how could you rule out MuSK MG in 1998, when it was only discovered in 2000?