While the Aromhum hernia model has been used previously to establish the role of E2/ESR1 signaling in LAM fibroblast activation, this study furthers our understanding of hernia pathogenesis by implicating P4/PGR signaling as an important downstream regulator of E2/ESR1-induced LAM fibrosis (12, 19, 20). The gene discussed is ESR1; the disease is lymphangioleiomyomatosis.