  In a recent paper by B. G. da Costa {\it et al.} [Phys. Rev. E 102,
062105(2020)], the phenomenological Langevin equation and the corresponding
Fokker-Planck equation for an inhomogeneous medium with a position-dependent
particle mass and position-dependent damping coefficient have been studied. The
aim of this comment is to present a microscopic derivation of the Langevin
equation for such a system. It is not equivalent to that in the commented
paper.
