Treatment of Langerhans cell histiocytosis bone lesions with zoledronic acid: a case series.

Langerhans cell histiocytosis (LCH) is a rare disease caused by a clonal proliferation of specialized dendritic (Langerhans) cells. Although uncommon, it is potentially fatal and carries significant morbidity. Bone involvement is particularly destructive and to date, no standard of care exists for management of both the disease and the significant bone pain as many of these patients experience. In the literature, 12 patients who had previously been heavily pretreated for their disease had their bone pain treated with a bisphosphonate as extrapolated from the cancer literature. Interestingly, these patients had a complete or near complete resolution of their pain, return of functional status and in 75% of cases radiographic evidence of reduction or regression of disease. Only 6 of these patients were treated with a newer generation bisphosphonate, zoledronic acid. In this paper, we report a case series of 2 patients with LCH bone involvement who received 4 mg of intravenous zoledronic acid monthly for 1 year with complete resolution in their bone pain. In addition, both patients demonstrated reduction in tumor burden after bisphosphonate treatment. Uniquely, our first case is the only reported case in the literature using a bisphosphonate as first line therapy in the treatment of LCH. This case demonstrates the potential role of zoledronic acid therapy in the first line setting for disease stabilization and symptomatic control in patients unable to receive conventional therapy.