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 EDTA plasma. When the cryoglobulin was incubated with fresh normal serum, almost complete conversion of C3, but not of factor B occurred.