[A rare case of bilateral femoral neck fracture in a 5-year-old girl with autosomal dominant osteopetrosis type 2].

The rare case of a 5‑year-old girl with autosomal dominant osteopetrosis type 2, who suffered metaphyseal fractures of the femoral neck on both sides within 6 months is described. On the right side, the diagnosis was made 3 months after the onset of symptoms, so that a coxa vara occurred. The treatment was surgically treated through a valgus osteotomy with fixation of the femoral head with K‑wires. Three months after the operation, the girl complained of a painful restriction of movement on her left side. Radiologically, a metaphyseal femoral neck fracture without coxa vara was diagnosed and in situ fixated with 2 K wires. Two months after the second operation, there was a symmetrical free range of motion of the hips with no symptoms. The metaphyseal femoral neck fracture with verticalization of the growth plate is a serious disease in autosomal dominant osteopetrosis due to the development of a coxa vara, which, if diagnosed at an early stage, can be treated well with in situ fixation. If the coxa vara has already developed, a valgus osteotomy should be performed despite the risk of delayed bone healing.