Muramidase (lysozyme) in joint fluid and serum of rheumatic patients

The muramidase activity of serum was studied in 27 cases of rheumatoid arthritis. The enzyme activity in rheumatoid serum (mean 11.0 mug./ml.) did not differ significantly from that in the 30 healthy controls (mean 9.4 mug./ml.). The muramidase activity in the synovial fluid of 36 rheumatoid arthritis patients was markedly elevated (mean 20.2 mug./ml.). In osteoarthritic synovial fluid (8 cases) the muramidase activity was low (mean 8.0 mug./ml.). No correlation was found between the total white blood count and the muramidase activity in rheumatoid synovial fluid. A positive relationship was observed between the enzyme activity and the total protein concentration. The elevated concentration of muramidase in synovial fluid of rheumatoid arthritis patients is interpreted as evidence of increased release of hydrolytic lysosomal enzymes. It remains to be shown which type of synovial fluid leukocytes produces the enzyme in question.