Langerhans cell histiocytosis (LCH) of bone is a benign-tumor-like osteolytic lesion in childhood and adolescence, which is characterized by the aberrant activation of antigen presenting cells. Rather than the multi-system involvements of LCH, no standard or widely-accepted therapeutic regimens were established for LCH of bone. In the previous clinical practice, several LCH patients obtained remarkable pain relief after taking prednisone. Therefore, the investigators aim to conducting a multi-center, open-labelled, randomized-controlled, Phase II study to investigate the efficacy and safety of oral prednisone in treating LCH of bone in children and adolescents. The enrolled patients will be randomly recruited to the following groups: (1) Oral prednisone \[Test group); (2) Regular observation \[Control group\].