CPT, Lorentz invariance, mass differences, and charge non-conservation
  A non-local field theory which breaks discrete symmetries, including C, P, CP, and CPT, but preserves Lorentz symmetry, is presented. We demonstrate that at one-loop level the masses for particle and antiparticle remain equal due to Lorentz symmetry only. An inequality of masses implies breaking of the Lorentz invariance and non-conservation of the usually conserved charges. 
A. D. Dolgov and V. A. Novikov
hep-ph