HPGDS and pulmonary fibrosis: In the lung, while studies on non-asthmatic models of pulmonary fibrosis acknowledge PGD2 itself (via its DP2 receptor) as either a beneficial [27–30] or a deleterious [31] signal against fibrotic development; in the asthmatic lung, however, PGD2/DP2 displays undisputable pro-fibrogenic impact [32,33].