Not only do MS individuals present a higher level of HERV expression than healthy individuals (Perron et al., 1997; Olival et al., 2013; Horssen et al., 2016), as well as HERV-W env protein was already detected in active white matter lesion of MS (Antony et al., 2004; Perron et al., 2005). Here, ERVW-1 is linked to myeloid sarcoma.