ERVW-1 and myeloid sarcoma: Phylogenetic study of HERV-W sequences derived from brain and peripheral blood mononuclear cells of multiple sclerosis (MS) patients provided by Mameli et al. showed that envelope gene intracellular domain of MSRV and ERVWE1 (syncytin-1) RNA share >89 % similarity while whole envelope gene showed >93 % similarity in both MSRV and ERVWE1.