Although patients diagnosed as Langerhans cell histiocytosis (LCH) with bone lesion initially respond well to treatment, some may experience relapse or refractory disease. Pamidronate, a potent N-bisphosphonate, has been used in several primary bone diseases, benign bone tumors, and metastatic bone cancers. The mechanism includes an inhibitory effect on osteoclast activity by decreasing development and recruitment of osteoclast progenitors and promoting osteoclast apoptosis. Herein, we introduce a seven-month-old Thai girl who was diagnosed as multiple-relapse LCH with refractory bone lesions and was treated with standard and salvage steroid-based therapies. After receiving two courses of intravenous pamidronate, she had marked clinical and radiographical improvement without any adverse events. She has been in remission for two years after receiving six courses of therapy. This report supports the efficacy of pamidronate in LCH-related bone lesions, but further studies in large cohort are warranted.

Keywords: Langerhans cell histiocytosis, Pamidronate, Refractory