While atoms can be comprised of antimatter the interactions are generally on a subatomic level, i.e. electron/positron, and proton/antiproton. Since particles/antiparticles are identical to their counterparts aside from charge any such interactions are total with nothing left over other than the resulting energy release usually in the form of photons. The results of an atom reacting with an anti-atom could have a variety of results depending on the differences in weight between the two. Exactly what those results might be is a bit beyond my lay-understanding of the process.