Cytology of Synovial Effusions in Epidemic Polyarthritis

Abstract

Examination of synovial fluid in 8 patients with epidemic polyarthritis following Ross Fiver virus infection showed cell counts ranging from 1500-13,800/mm3. Stained smears were notable for a paucity of neutrophils and high proportions of monocytes and vacuolated macrophages; they were further characterized by light microscopy and EM. Ross River virus antigen was detected by specific immunofluorescence in monocytes and macrophages of 4 cases early in the course of the illness; intact virus was not identified by EM or cell culture. No cell-associated C3 component of complement, IgM or IgG was detected in any cell-type. Cell counts and simple smears may be useful in the early diagnosis of suspected epidemic polyarthritis and provide further information pertinent to the pathogenesis of this disease.