cryoglobulin 

A circulating protein, specifically immunoglobulin (i.e. IgG, IgM, IgA, or light chain), that clumps together or precipitates when exposed to cold and dissolves when warmed.
They may be present in small quantities in the blood of some healthy people but are most frequently associated with abnormal protein production and a variety of diseases and conditions like inflammation and organ damage.
cryoglobulin test: To detect the presence and relative quantity of cryoglobulins in the blood.
cryoglobulinemia: Presence of large amounts of cryoglobulins in the blood, that can slow the flow of blood and block small blood vessels. Symptoms include bruising, rashes, joint pain, weakness, Raynaud phenomenon, skin ulcers, and gangrene.