Welcome to the forum.
In general, anonymous sex between men is pretty high risk for syphilis. However, the evidence is overwhelming that's not what you have. 1) Although oral-genital syphilis transmission can occur, it isn't very common. 2) If you had caught syphilis, the initial sign would be an open sore of a directly exposed area -- in this case your penis or mouth. 3) A dermatologist's diagnosis of pyityriasis rosea is highly accurate. Although PR can be confused with secondary syphilis, few dermatologists would confuse them. 4) It is only the rash of secondary syphilis that is sometimes confused with PR, and secondary syphilis does not occur sooner than 3 months after exposure.
If you want further reassurance, you can always have a syphilis blood test; the test is accurate any time 6 weeks or more after exposure. But I really don't think it is necessary; you can definitely rely on the dermatologist's diagnosis.
I hope this helps. Best wishes-- HHH, MD
Thank you very much! I fully understand and appreciate that anonymous gay sex is risky and I can assure you that it will never happen again. Although petrifying, it was a valuable lesson learned. Thanks again for your insight.
I saw this before replying. It makes no difference in my opinion or advice.
I should add that I have never had any unprotected anal sex and I do not frequently meet guys for discreet encounters. Last discreet encounter was January 2011 and March 2011.