Clinical findings and immunochemical studies in a patient with cryoglobulinaemia

Purpura, shallow ulcers, and livedo were noted in a patient with IgG3-kappa cryoglobulinaemia. The IgG3 cryoglobulin reacted with all IgG subclasses. No complement activation could be demonstrated in fresh normal serum, almost complete conversion of C3, but not of factor B occurred.