Segre varieties and Lie symmetries

We show that biholomorphic automorphisms of a real analytic hypersurface in Cn+1 can be considered as (pointwise) Lie symmetries of a holomorphic comp letely overdetermined involutive second order PDE system defining its Segre family. Using the classical S.Lie method we obtain a complete description of infinitesimal symmetries of such a system and give a new proof of some w ell known results of CR geometry.