  A simple extension of the minimal renormalizable supersymmetric SO(10) grand
unified theory by adding a 120-dimensional Higgs representation is examined.
This brings new antisymmetric contributions to the relevant quark and lepton
mass sum rules and leads to a better fit of the measured values of lepton
masses and mixings together with a natural completion of the renormalizable
Higgs sector within the SUSY SO(10) framework.
