The abnormal monoclonal IgM can cause neuropathy as an autoantibody against myelin-associated glycoprotein, autoimmune cold hemolytic anemia when directed against its own RBC antigen, deposit in extracellular space of various organs as amorphous material often with a combination of amyloid, precipitate in cold manifesting symptoms of cryoglobulinemia. The gene discussed is CD40LG; the disease is cryoglobulinemia.