I had never heard of TOS (thoracic outlet syndrome) prior to signing up to the sorehand mailing list.
There are several participants who write about their TOS and the importance of having it properly diagnosed. You wouldn't want to think you have RSI and actually have TOS, after all.
What on earth is TOS, I wondered.
This link seems to explain it quite well:
http://www.answers.com/topic/thoracic-outlet-syndrome
And the syndrome does seem to be a genuine medical diagnosis.
But, with all the varying diagnoses going around, I think that the dangers of self diagnosis by Internet are definitely there.
Between fibromyalgia, RSI, TOS, TMS, Tendonitis, carpal tunnel syndrome etc having similar symptoms, I really do think that you need a doctor who can rule out what you don't have and help you manage what you do have.