[Mixed cryoglobulinemia with monoclonal IgA and biclonal IgM during hepatitis C virus infection].

Cryoglobulins are immunoglobulins that precipitate at low temperature and dissolve when warmed. According to Brouet, their classification relies upon the immunochemical study: type I comprises monoclonal immunoglobulins (IGG), when types II and III include both monoclonal and polyclonal components. During C hepatitis, the presence of a cryoglobulin, essentially made of mixed G-IGG and M-IGG, is a common feature with a prevalence of 40 to 80%. The authors report a case of a 63-year patient who presented with a vascular purpura and a peripheral polyneuropathy in a context of C hepatitis infection. The cryoglobulin found was composed of a monoclonal kappa A-IgG associated with a biclonal kappa and lambda M-IgG. No decrease of normal IgGs was found. This type of cryoglobulin does not belong to Brouet's classification, and argues for a new and more pertinent classification to be proposed.