Expression of misfolded cartilage oligomeric matrix protein (COMP) in proliferating and hypertrophic chondrocytes results in chondrocyte disorganization and causes Pseudoachondroplasia (PSACH), suggesting triggering the UPR may underlie many chondrodysplasias where mutations cause accumulation of misfolded proteins (Posey et al., 2012; Piróg et al., 2014). The gene discussed is COMP; the disease is pseudoachondroplasia.