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. Slit lamp examination showed crystals in Bowman's membrane. Plasmapheresis led to temporary improvement in the synovitis and tenosynovitis.