  In models with flavour symmetries added to the gauge group of the Standard
Model the CP-violating asymmetry necessary for leptogenesis may be related with
low-energy parameters. A particular case of interest is when the flavour
symmetry produces an exact mass independent lepton mixing scheme, leading to a
vanishing CP-violating asymmetry. We present a model-independent discussion
that confirms this always occurs for unflavoured leptogenesis in type I see-saw
scenarios.
