Pseudoachondroplasia (PSACH) is a severe inherited dwarfing condition In PSACH, a genetic mutation leads to abnormal retention of cartilage oligomeric matrix protein (COMP) within the endoplasmic reticulum (ER) of cartilage-producing cells (chondrocytes), which interferes with function and cell viability. Investigators describe how this protein accumulation results in ‘ER stress’ and initiates a host of pathologic changes. These findings may open up new ways to treat PSACH and other ER-stress-related conditions.