Cryoglobulinaemia may be discovered by systematic blood examination or by the finding of a purpura reflecting a leukocytoclastic angiitis or vascular manifestations. An immunochemical study is necessary to determine whether the cryoglobulin thus found is purely monoclonal or mixed, with a monoclonal component (usually IgM) and a polyclonal IgG component, or is composed of polyclonal immunoglobulins. The principal complications of cryoglobulinaemia involve the kidneys and the nervous system. Monoclonal cryoglobulins may reveal Kahler's disease or Waldenström's macroglobulinaemia. Mixed cryoglobulins are often associated with autoimmune or infectious diseases, such as Epstein-Barr virus infection or hepatitis C. Treatment is difficult. In severe forms of cryoglobulinaemia plasmapheresis and chemotherapy can be used.