Experimental lathyrism: exostoses and aneurysmal-like bone cysts of the mandible in the rat.

The effect of chronic lathyrism on the mandible of the rat was studied. Exostoses, thinning and discoloration of the cortical plates, intraosseous bleeding and hemorrhagic cyst were observed after six weeks of administration of beta-aminoproprionitrile fumarate. The exostoses consisted of homogeneous cellular fibrous tissue containing osteoid, hyalin-like material and abundant ground substance. The cysts were filled with erythrocytes and lined by spindle-shaped fibroblasts, collagen fibers or osteoblast-like cells. Between the cysts, bands and sheets of dense and cellular connective tissue presenting foci of hemorrhage, osteoid and metaplastic cartilage were found. Numerous mast cells were demonstrated with alcian and toluidine blue in the hematopoietic bone marrow, cancellous bone and around the capillary network surrounding the exostoses and cysts. Exostoses have already been studied and explained by the action of BAPN (lysyl oxidase). Hemorrhagic cysts could be explained by histamine release from the mast cells (hypervascularity, hyperemia, increased permeability, rupture and progressive confluence of these small hemorrhagic cysts). Histopathology of the experimental cysts had some points in common with the human aneurysmal bone cyst. Could the pathogenic mechanisms be similar for both lesions?