  A predictive framework for fermion masses and mixing is given by the
supersymmetric SO(10) model with one 10, one bar126, one 126 and one 210 Higgs
representations, and type II seesaw dominating the neutrino mass matrix. We
investigate the origin of the tension between this model and lepton mixing data
and refine previous numerical analyses. We discuss an extension of the minimal
model that includes one 120 Higgs chiral superfield representation. This
exhausts the possible renormalizable contributions to the Yukawa sector. In
spite of the increase in the number of parameters the predictivity of the
minimal setting is not spoiled. We argue that the contributions to fermion
masses due to the doublet components of 120 can be naturally small compared to
those of 10 and 126, thus acting as a perturbation in the fermion mass
generation. The antisymmetric nature of the 120 Yukawa coupling affects at
leading order the determination of the mixing angles and it allows to remove
the inconsistencies between predictions and data on the neutrino parameters. An
improvement in the experimental bound on |Ue3| can tell this scenario from the
minimal model.
