[Cellular aspects of reorganization of pagetic bone tissue]

The light microscopy features of the cellular reorganisation of tone tissue in Paget's disease are well known. They result in the constitution of abnormal bone tissue. Ultrastructural studies have enabled a more detailed study of osteoblasts, osteocytes and osteoclasts. Osteoclasts are the only cells which present abnormalities. In particular, we observe intranuclear and intracytoplasmic inclusions composed of microcylinders. The morphological analysis is able to relate the presence of these formations with a viral infection of the paramyxovirus group. The results obtained by immunocytochemical techniques support this hypothesis. The osteoclast lesion could be a determining factor in the abnormal reorganization of bone tissue in Paget's disease, which may be considered to be a disease due to a slow acting virus.