Therefore, PASC-PF is characterized by the sustained loss of functional alveolar epithelial cells, and the persistence of metaplastic Krt5+ cells, Krt8hi transitional cells, and Krt5−Krt17+ aberrant basaloid cells, which is histologically akin to other fibrotic lung diseases such as idiopathic pulmonary fibrosis (IPF) (Extended data Fig. 2b,c) (30, 31). The gene discussed is KRT5; the disease is idiopathic pulmonary fibrosis.