The value of biopsy in patients with monarticular juvenile rheumatoid arthritis of recent onset

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Abstract
The histopathology of arthroscopic biopsy material from the knees of 8 patients with monarticular juvenile rheumatoid arthritis (JRA) of recent onset and of 4 control patients was examined using a histochemical method for acid α‐naphthyl acetate esterase and an avidin‐biotin‐peroxidase complex method for different cell subtype‐specific surface antigens. According to results of our prospective, single‐blind study, nonspecific synovitis was observed in those biopsy samples obtained early in the course of disease. The samples were also characterized by cellular changes that are quite distinct from those described in patients with chronic rheumatoid synovitis. JRA must be considered the cause of symptoms if no orthopedic or infectious disease is found at arthroscopy in children with monarticular symptoms of recent onset and if nonspecific synovitis is observed in the histopathologic specimen. This pathologic description, however, does not correspond to that of classic rheumatoid synovitis. In our studies, we found that mononuclear cells displaying diffuse cytoplasmic esterase and surface Ia formed a large proportion of all inflammatory cells in situ. There were comparatively few activated Ia+ T cells and plasma cells. These observations suggest that exudative features and nonspecific cellular inflammation are prominent at onset of JRA. The immune response, in the form of immunocompetent T and B cells, seems to be more extensively involved in chronic JRA and may represent secondary features of the disease.