Expansion of one of the three EC subtypes, probably corresponding to post-capillary venular cells, was observed in human skin samples from patients with atopic dermatitis or psoriasis.86 In idiopathic pulmonary fibrosis (IPF), the peribronchial EC population was increased compared to control or obstructive pulmonary disease conditions and associated to areas of bronchiolization and fibrosis, showing the distinct response of this population between two diseases.52 In mouse lungs exposed to hyperoxic conditions, an increase of the aerocytes/Car4+ ECs population was observed.87 Here, CA4 is linked to idiopathic pulmonary fibrosis.