Biochemical markers of bone turnover, serum levels of interleukin-6/interleukin-6 soluble receptor and bisphosphonate treatment in Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare non-Langherans form of histiocytosis characterized radiologically by symmetrical sclerosis of the metaphysis and the diaphysis of long tubular bones. Macrophages are potent interleukin-6 (IL-6) producers and elevated IL-6 serum levels have been described in pathological conditions characterized by increased bone resorption. In a patient with ECD, during the acute phase of the disease we found high serum levels of IL-6 and IL-6 soluble receptor (sIL-6R) and high levels of bone turnover markers. After 5 years of combination therapy with oral prednisone and intravenous clodronate a significant reduction in the above mentioned biological parameters was seen. We suggest that the systemic disorders present in ECD could be related to the high serum levels of IL-6 and sIL-6R. We also propose the use of bisphosphonates in the clinical management of ECD.