IFITM5 and osteogenesis imperfecta type 5: As the skeletal phenotype caused by heterozygous mutation in IFITM5 differs between mouse and human, it is difficult to extrapolate the effects of FK506 or rapamycin on human OI type V. However, the findings obtained in this study are expected to enable elucidation of the mechanism by which MALEP-IFITM5 causes skeletal anomalies and provide essential information for development of therapeutic strategies.