Treatment of ANCA-Negative Small Vessel Vasculitis

Cryoglobulinaemia refers to circulating cryoglobulins. Cryoglobulins are immunoglobulins, which precipitate in temperatures below 37oC and dissolve upon rewarming [2]. Cryoglobu‐ linaemia is classified in 3 types based on clonality and immunoglobulin class. In particular, type I consists of monoclonal IgM or IgG immunoglobulin, type II is a mixture of monoclo‐ nal IgM and polyclonal IgG, while type III is a mixture of polyclonal IgM and IgG. Type II and III are also called “mixed”, since both contain a mixture of IgM and IgG immunoglobu‐ lins [3]. The IgM component of type II cryoglobulins has rheumatoid factor activity (can bind to the Fc portion of IgG). All 3 types of cryoglobulinaemia may or may not result from an underlying disorder. In the absence of an identifiable cause cryoglobulinaemia is charac‐ terized as “essential”.