Cryoglobulins are classified into three types: type I cryoglobulinemia involves monoclonal immunoglobulin, usually immunoglobulin M (IgM) or, less frequently, immunoglobulin G (IgG) or light chains; types II and III cryoglobulinemia (mixed cryoglobulinemia) are immune complexes composed of monoclonal (type II) or polyclonal (type III) immunoglobulin (IgM) with rheumatoid factor (RF) activity [3]. This evidence concerns the gene CD40LG and cryoglobulinemia.