  The random--anisotropy Blume--Emery--Griffiths model, which has been proposed
to describe the critical behavior of $^3$He--$^4$He mixtures in a porous
medium, is studied in the pair approximation of the cluster variation method
extended to disordered systems. Several new features, with respect to mean
field theory, are found, including a rich ground state, a nonzero percolation
threshold, a reentrant coexistence curve and a miscibility gap on the high
$^3$He concentration side down to zero temperature. Furthermore, nearest
neighbor correlations are introduced in the random distribution of the
anisotropy, which are shown to be responsible for the raising of the critical
temperature with respect to the pure and uncorrelated random cases and
contribute to the detachment of the coexistence curve from the $\lambda$ line.
