The cryoglobulin test detects antibodies in the blood that may cause sensitivity to low temperatures. Cryoglobulins may be divided into three classes.
- Type I are monoclonal immunoglobulins, usually IgG or IgM, infrequently IgA, and are usually associated with lymphoproliferative disorders, especially macroglobulinemia or multiple myeloma. These are usually present in high concentrations.
- Type II cryoglobulins are mixed cryoglobulins consisting of two or more immunoglobulins of different classes, one being a monoclonal protein (with a high proportion being IgM), and the other a polyclonal IgG.
- Type III cryoglobulins are also mixed cryoglobulins consisting of two or more immunoglobulins of different classes, however, each component is a polyclonal immunoglobulin. These are usually present in low concentrations (<1%), and are associated with various autoimmune diseases, chronic active hepatitis, and other viral infections.
All types of cryoglobulins may be responsible for specific symptoms that occur in response to cold weather, such as Raynaud’s phenomenon, vascular purpura, bleeding tendencies, cold-induced urticaria, and even distal arterial thrombosis with gangrene.