Proliferative synovitis in hemophilia: biochemical and morphologic observations.

The synovium removed from the knee of a 10-year-old with hemophilia A was characterized morphologically and biochemically. The specimen showed villous hypertrophy with hyperplasia of synovial lining cells which contained abundant intracytoplasmic granules of hemosiderin. Monolayer cultures prepared from enzymatically dispersed tissue were characterized by pigment-laden fibroblast-like cells and round cells. Both explants of synovium and adherent cells secreted a large amount of latent collagenase and neutral proteinase into the culture medium. The secretion of these enzymes dropped sharply and intracellular pigment decreased with passage of these cultures. Lysozyme was secreted by the explants but was not detected in the monolayer culture medium. These data establish the degradative potential of the synovitis found in hemophilia and support the concept that recurrent hemarthrosis without inflammation is sufficient in and of itself to produce proliferative synovitis.