In OI patients, the presence of MCSF and RANKL determined an increased secretion of CK-BB from osteoclasts (p = 0.04) compared with control conditions without these cytokines; interestingly, in the absence of these factors, the secretion of CK-BB is significantly elevated at 3 μmol/L compared with 0.03 and 1 μmol/L (p = 0.007). This evidence concerns the gene TNFSF11 and osteogenesis imperfecta.