[The pathogenesis of erysipelas arthritis]

Experimental chronic erysipelas polyarthritis in rat, induced by living erysipelas bacteria, histologically can be divided into four different phases. In the phase of population bacteria are distributed diffusely within the whole joint but accumulate in the transitional zones and entheses by multiplication within the ground substance of cartilage. In the phase of acute destruction a severe inflammation of all joint tissues predominates. Bacterial antigen is eliminated by a pannus tissue destroying the cartilaginous structures. In the following phase a diffuse dystrophy of articular cartilage dominates. The reason for this process is not clear; within the cartilage bacterial antigen can seldom be demonstrated, but it accumulates intracellularly in the periphery of the joints (e.g. dense connective tissue, muscles). In the chronic phase we find a lymphoplasmacytic infiltration of the subsynovium, a lining cell hyperplasia, and pannus formation arising from the epiphyseal bone marrow cavity. The relation between chronic inflammation and destruction in the central and antigen persistence in the outer parts of the joints is a matter of current investigation.