摘要To the Editor:Heterotopic ossification (HO) is a formation of bone outside of the skeletal system.It usually occurs in the following five broad clinical settings:genetic,posttraumatic,neurogenic,postsurgical and as distinctive reactive lesions most often seen in the hands and feet.[1] Although there is an increased tendency to bleed in soft tissue,HO has rarely been reported in hemophilia.At present,a few cases reported the location relationship between ectopic osteogenesis and the pelvis,and only two cases presented pelvi-femoral bone bridge-like progression of this phenomenon.[2.3] More precisely,it was situated in the posterior area of the hip joint.Here,we describe a rare case of HO bridging from the anterior superior spine to the lesser trochanter of the femur in hemophilia.