RARA and myeloid leukemia: Interestingly, topical tazarotene treatment improved X‐linked ichthyosis, caused by deficiency of steroid sulfatase, activated by FGE, and retinoid treatment increased STS activity via RARα and RXR receptors involving PI3 kinase and ERK‐MAP kinase pathways in myeloid leukemia cells that have been discussed to evolve from FGE activity increase (Hofmann et al, 1999; Hughes et al, 2006).