I've got two tattoos, both of which I got since developing RSD.

I didn't have any problems with either tattoos. No spreading etc. The one thing I will say though is that I wouldn't ever have one on an RSD limb. For me, injections in the limbs that have RSD causes major problems (one time it caused me to be unable to walk and the next I got myoclonic jerks) so I would never have anything done in those areas that wasn't needed.

Good Luck if you go ahead with getting a tattoo. Follow the advise for cleaning them etc.