In IPF patients, nuclear PRRX1-positive cells were mainly detected in the fibroblast foci (also observed by others Yeo et al., 2018) which are the active sites of fibrogenesis (Fernandez and Eickelberg, 2012; Martinez et al., 2017) and in scattered mesenchymal cells within the remodeled / fibrotic lung areas (Figure 1D). The gene discussed is PRRX1; the disease is idiopathic pulmonary fibrosis.