An intriguing finding in PACS cases of this series was the occurrence of morphological and immunophenotypical changes in the pulmonary vascular bed, similar to those observed in acute early/mild cCOVID-19 pneumonias (vascular enlargement and abnormal endothelial expression of IDO1, PD-L1 and STAT3) [35,36]. The gene discussed is IDO1; the disease is pneumonia.