I don't find much info on this, so I'm posting my own experiences, in case it helps anyone else in a similar situation.
I've somehow acquired Tourette's as an adult, in my early 40's. I've no history of TS symptoms as a child---I was a rabid nail-biter, but definitely no twitching, compulsions or anything else. Well-behaved, quiet, did very well in school, etc.. No obvious family history of anything related either (although limited family history is available).
The acquisition was not sudden, although the main impact was. I did some minor leg twitching in the throes of appendicitis many (10?) years ago, but that only lasted for a few hours while I was in emergency--I'm not even sure it's relevant. The real problems began around 4 years ago when I started having brief and small leg spasms sometimes at night while watching TV. This slowly increased over about 9 months, but was still at best a couple of twitches per night, only a curiosity. I then came down with some kind of chest infection, which accelerated things---one day I started twitching violently, lost control of emotions, had trouble breathing etc. I had several such major episodes over a span of a few weeks, with reducing severity. At the same time, however, much smaller arm, leg and head spasms started showing up.
The major episodes disappeared altogether, but the twitches kept increasing in frequency. I used to count them on my way to work, about a 25 minute walk. At first it was just 5-10 tics, then went up to 20, then up to 80, then up to 200, and then I gave up because I kept losing count, and wasn't sure if I was maybe just starting to twitch due to counting. Nowadays I twitch every 1-3 seconds; sometimes I feel like I'm vibrating. Initially these were just motor tics (head shakes, arms, legs suddenly flying out etc), but after several more months some minor vocal tics appeared. These are now fairly common, although still only a small fraction of the motor ticks. (More complex vocal tics have started to appear recently, but are not yet an issue, and hopefully won't be.)
I spent about a year and half being investigated for everything under the sun, getting test after test. My neurologist then was sure I had some kind of myoclonus or epilepsy, and I tried several medications, none of which helped (and all of which were unpleasant in side effects). It took almost another year to get an appointment with a neurologist that specialized in movement disorders. They immediately declared I had Tourette's, and also told me that adult onset was extremely rare, and little could be done. I tried a couple more medications (dopamine aggressors), but these actually did nothing. I haven't seen a doctor for well over a year, maybe 2.
I had strong doubts of the TS (more strictly speaking TD-NOS aka "Tic Disorder Not Otherwise Specified") diagnosis, mainly because when I read up on TS people were talking about holding back tics for hours. I can hold them back for maybe 15 seconds. I rarely have a sense of premonition (but do get a sense of build-up when trying to hold it back). That doesn't mean they're constant---when I'm talking to someone, working intensively etc my tics reduce dramatically, almost completely disappearing. But I have to be talking or very very intensely paying attention---it seems to be largely an affliction of self-awareness. There is also a sensory component, everything makes me jump, I feel constantly surprised, and the world is very bright indeed. If I had to describe it one sentence, I'd say the world has been turned up to 11.
Despite all this, and after some initial adjustment, it hasn't ruined my life. I looked at the Yale Tic severity test, and while I score around a 40/50 in tic severity, I'm only maybe a 50/100 overall--the overall life impact is small, at least so far. Walking is definitely harder, I avoid any situation where I have to sit passively, etc. But these are small things. I've also found a few coping techniques, eg by keeping one part of my body active/in-motion I can prevent tics in another part, at least for a while. I guess I've become good at disguising it too (apparently my head is very itchy).
Anyway, that's the gist of it. There's obviously some O from OCD creeping in too, and the tics are in a constant evolution (my legs almost never twitch unless I'm actually walking, and I no longer get easily "stuck" half-way through a fine-motion, but I've acquired more vocal behaviours). I don't know what is going to happen in the future; at the moment the worst I expect are problems stemming from the mechanical wear associated with constant, violent movements. My optimistic view is based on the fact that many to most childhood cases of TS seem to run their course in 10 years-ish, so maybe that will happen for me too---why not, this came from nowhere so it could go back there at any time too.