Arthritis associated with a crystallizing cryoprecipitable IgG paraprotein.

A crystallizing IgG-lambda cryoprotein was found in the synovial fluid of a patient with peripheral erosive arthritis and tenosynovitis. The same crystallizing paraprotein could be demonstrated in serum incubated at 4 degrees C, but its formation could be inhibited by the in vitro addition of D-penicillamine. Crystals were present in synovial tissue and appeared to be initiating an inflammatory reaction via complement activation.