Multifocal sclerotic lesions in Erdheim-Chester disease successfully treated with tocilizumab.

A 58-year-old woman presented to the outpatient clinic with invalidating bone pain in the proximal lower extremities. Laboratory testing showed increased inflammation parameters with a normocytic anemia. Bone scintigraphy revealed increased uptake in both radii, distal femurs, tibiae, and fibulae. PET/CT scanning showed irregular sclerotic bone lesions without other abnormalities. Multiple bone biopsies showed histiocytes expressing CD68 and Factor XIIIa. Metastatic or hematopoietic neoplasms were ruled out. A diagnosis of Erdheim-Chester disease (ECD) with solely osseous involvement was made. Treatment with tocilizumab weekly, an IL-6 receptor antibody, was successful. Tocilizumab appears to be a promising agent for the treatment of patients with Erdheim-Chester disease with limited organ involvement.