AUTS2 was already known to influence brain development. Our study uncovers a crucial link between disruptions in the AUTS2 gene and a rare skeletal disorder characterized by fused forearm bones (radioulnar synostosis, RUS), where the radius and ulna fail to separate properly. By studying four unrelated patients, we identified different genetic alterations in AUTS2, all leading to this forearm fusion along with other skeletal features like short stature, jaw abnormalities, and hip dysplasia. These findings reveal AUTS2’s previously unknown role in bone development, particularly in forming the elbow joints. This discovery not only improves diagnosis for patients with RUS but also deepens our understanding of how genetic changes can affect skeletal formation, paving the way for better genetic counseling and future therapies. This “one gene, multiple effects” phenomenon (called pleiotropy) highlights how genetic changes can manifest differently in each individual. (By Dr. Yongjia Yang, https://jmg.bmj.com/content/early/2025/07/16/jmg-2025-110886 )