CHI3L1 and Hermansky-Pudlak syndrome: In HPS pathophysiology, the chitinase-like-protein CHI3L1 and its impaired interplay with its receptor CRTH, a non-chemokine chemoattractant GPCR with a preference for Gαi proteins, seems to play an important role, although the exact causal molecular pathways in HPS are still understudied [45].