Experimental bone marrow fat necrosis.

We have studied serially by light and electronmicroscopy the development of lesions of the adipose tissue of the bone marrow of the rabbit following intravenous injections of saponin. Two types of steatonecrotic lesions were seen: in the femur giant-cell granulomas surrounding necrotic fat cells and in the sternum, small foci of fat necrosis containing calcified deposits. In both cases the lesions were of ischemic origin and secondary to the destruction of the microcirculation of the bone marrow by saponin. These studies suggest that necrosis of the bone marrow fat cells can contribute to the pathogenesis of myelofibrosis. They also suggest that adipose tissue responds differently to ischemia depending on topography. In hematopoietic marrow necrosis of fat cells is followed by calcium deposits, whereas in fatty marrow necrosis leads to resorptive giant cell reaction.