  In this paper we generalize an equation studied by Mossino and Temam, to the
fully nonlinear case. This equation arises in plasma physics as an
approximation to Grad equations, which were introduced by Harold Grad, to model
the behavior of plasma confined in a toroidal vessel. We prove existence of a
$W^{2,p}$-viscosity solution and regularity up to
$C^{1,\alpha}(\overline{\Omega})$ for any $\alpha<1$(we improve this regularity
near the boundary). The difficulty of this problem lays on a right hand side
which involves the measure of the superlevel sets, making the problem nonlocal.
