Disappearing bone disease is a rare condition and usually affects young adults. Its aetiology is not known. A case of a 12-year-old female child, who had a fall and sustained a fracture mid shaft of femur and supracondylar region, is reported. On follow-up subsequent X-ray showed extensive osteolysis which was progressively affecting the other side of the pelvic girdle and femur. She was put on trial of calcitonin 50 IU by nasal spray for six months but there was no improvement. However, during the past three and half years the disease process had progressively extended to the other side of pelvic girdle and femur with fatal outcome. To the knowledge of the authors such progression in a short time has not been reported in any case so far.