Why is graft-versus-host disease a consideration in Lichen planus-like eruptions?

Graft-versus-host disease (GVHD) is a complication of allogeneic bone marrow transplantation. In GVHD, the immune effector cells of the donor bone marrow (the “graft”) react against antigens of the recipient tissues (the “host”). The resultant eruption may be indistinguishable, both clinically and histopathologically, from that of LP. Lichenoid GVHD reaction is often more generalized than is classic LP, and the history would certainly be suggestive. GVHD resulting from solid-organ transplantation is exquisitely rare.

Johnson ML, Farmer ER: Graft-versus-host reactions in dermatology, J Am Acad Dermatol 38:369–392, 1998.