ERN1 and Schmid metaphyseal chondrodysplasia: Cameron et al. analyzed the role of the IRE1α/XBP1 pathway in the pathology of Schmid-type metaphyseal achondroplasia (MCDS) and proposed that the pathology of MCDS is supported by XBP1-independent UPR-induced dysregulation of C/EBP-β-mediated chondrocyte differentiation11.