Cryoglobulins are antibodies that precipitate below ~37°C. Especially in body parts that can be very chilled (face, fingers, toes etc) there is a chance that these antibodies precipitate in vivo and cause obstruction and inflammation of blood vessels. The antibodies of type IgG, IgM or IgA can be either monoclonal or polyclonal in nature. Cryoglobulins occur in lymphoproliferative diseases such as Multiple Myeloma or CLL, chronic or acute infections or in autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematodes (SLE).

Complexes can be phagocytosed by neutrophils but can also be seen as free precipitates in the smear.