The serum DKK1 concentration was 5.20 (4.54, 6.32) ng/mL in children with OI, which was significantly higher than that of healthy children [4.08 (3.59, 4.92)] ng/mL (P < 0.001) (Fig. 2a). The gene discussed is DKK1; the disease is osteogenesis imperfecta.