Essential cryoglobulinemia associated with intense and persistent synovitis of the knee

Two patients with essential cryoglobulinemia, an immune complex disease, developed an intense, chronic, monoarticular knee synovitis. In each patient, synovial fluid findings (high white count and left shift) suggested a pyrogenic or crystalline etiology. A synovectomy was eventually performed in both patients to control their synovitis, which was refractory to medical management. The histologic and immunofluorescent synovial changes in the arthropathy of essential cryoglobulinemia, which was not previously been characterized, are marked by diffuse eosinophilic infiltration and edema. In both patients, synovial specimens suggested an immune complex process; immunofluorescent studies revealed immunoglobulin IgG in one patient, and IgG, IgA, and immune complexes (C1q) deposits in the other patients. Both patients, subsequently treated with D-penicillamine and chloroquine, or chloroquine alone, were followed for two years and had a slow but definite fall in their cryoglobulin levels, despite the persistence of monoarticular synovitis in one patient.