  We try to explain the spatial variation of primordial deuterium suggested by
some observations by varying leptonic chemical potentials. The variation of the
latter may take place in some scenarios of leptogenesis. The model predicts a
large mass fraction of $^4 He$ (35-60%) and $^7 Li$ (up to $10^{-9}$) in
deuterium-rich regions. Because of lepton family symmetry, the angular
variations of cosmic microwave background radiation can be sufficiently small
although still observable in future measurements.
