I can't speak for every country but in most of Europe the opposite is the case. You'll be asked for preexisting conditions - but only once you register for medical care, and only to ensure good information and proper care. For immigration the main concern will be whether you have the means to support yourself (i.e. a job in the country or independent wealth) and whether you are assimilated (language, culture) before you get permanent residency or nationality.

In most EU countries even tourists can receive free/cheap care at public hospitals - but check for the specific country before you travel.