Patients with the RAR loss of function (LOF) mutant exhibited osteopetrosis-like symptoms.41,42 Retinoic acid relieved osteopetrosis symptoms by activating osteoclastogenesis in animal models and some patients.17,18 Our previous study indicated that osteoblastic retinoic acid signaling inhibition caused craniofacial deformity.23 In this research, we further explored phenotype redouts, such as long bones, and the hematopoietic and immune systems, and increased bone density and brittle bone were detected. The gene discussed is RARA; the disease is osteopetrosis.