A case of spontaneous femoral neck fracture associated with multicentric reticulohistiocytosis. Oversecretion of interleukin‐1β, interleukin‐6, and tumor necrosis factor α by affected synovial cells

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Abstract
We describe a case of left femoral neck fracture associated with multicentric reticulohistiocytosis (MR). Biopsy specimens from a skin nodule and from synovial tissue showed histiocytic multinucleated giant cells (MR cells) that are characteristic of MR. A surgical specimen from the resected femoral head revealed that multinucleated giant cells and mononuclear cells invaded the marginal subchondral bone, without evident pannus. These cells also infiltrated into the fracture site, with bone resorption by activated osteoclasts. Immunohistochemical studies of synovium from the left hip joint showed positive staining for interleukin-1β (IL-1β), IL-6, and tumor necrosis factor α, and abundant cytokine production by cultured synovial cells was demonstrated. These findings suggest that the subchondral invasion and intramedullary infiltration by MR cells caused articular destruction and/or fracture as a result of oversecretion of the cytokines.