“…Ultrastructural studies have shown the presence of specific inclusions in the enormous, multinucleated osteoclasts from Pagetic bone tissue. Morphological analyses have demonstrated that the structure, the dimensions and the cytoplasmic and nuclear distribution of the microcylindrical inclusions observed in Pagetic osteoclasts are very similar to the nucleocapsids found in cells infected with paramyxoviruses (Gherardi et al, 1980;Harvey et al, 1982;Howatson & Fornasier, 1982;Mills & Singer, 1976;Rebel et al, 1980bRebel et al, , 1974. Furthermore, using immunocytological techniques with polyclonal antibodies, several studies have demonstrated that osteoclasts from bone tissue in Paget's disease contain antigenic material related to measles virus and to respiratory syncytial virus, both of which are members of the family Paramyxoviridae (Basl6 et al, 1979;Mills et al, 1982;Rebel et al, 1980a;Singer & Mills, 1983).…”