Lichenoid Chronic Graft-vs-Host Disease Following Blaschko Lines

Psoriasiform graft‐versus‐host disease distributed along Blaschko's lines

“…In addition to its rare morphologic appearance, this case presents a unique pattern of distribution along lines of Blaschko, which is a rare form of linear cGVHD and of which there are also few reports in the literature . The lines of Blaschko represent the migration of embryonic cells in the skin, and are otherwise unseen unless there are variations of DNA sequencing or gene expression in these cell lines.…”

“…Such variations may then manifest in the typical whorled pattern associated with the path of the cells’ migration. The prevailing theory accounting for cGVHD occurring in a Blaschkoid fashion proposes that the donor lymphocytes expose a somatic mosaicism in the host cells; this mosaicism had previously been tolerated by the host's own lymphocytes and was therefore masked . The donor cells target the host's genetically varied cells, which have migrated in a particular pattern over time, thus resulting in a swirling presentation of cGVHD.…”

Blaschkoid Acute Graft-vs-Host Disease

“…A blaschkoid pattern is characteristic of epidermal nevi and some genodermatoses, but it has also been noted in several acquired inflammatory dermatoses including vitiligo, lichen planus, psoriasis, morphea, lichen sclerosus, lupus erythematosus, and drug eruptions . Blaschkoid chronic GVHD has been reported infrequently, manifesting as lichenoid and rarely as a psoriasiform eruption . Many of these patients had prior acute GVHD, but this was not reported to be in a blaschkoid pattern.…”

“…A postzygotic mutation in a clone of migrating epidermal cells would manifest itself along the lines of Blaschko. It is hypothesized that in some people, this postzygotic mutation is clinically silent until donor lymphocytes from a bone-marrow allograft attack the mutated cells resulting in a blaschkoid pattern of GVHD . The development of linear GVHD has also been ascribed to an isotopic phenomenon at sites of previous herpes zoster eruption .…”