Autoimmune haemolytic anaemia with monoclonal IgM (kappa) anti-P cold autohaemolysins.

A patient is described with immunoblastic non-Hodgkin's lymphoma and autoimmune haemolytic anaemia of the cold autoantibody type. The autoantibodies were monoclonal IgM-kappa cold haemagglutinins/haemolysins with blood-group specificity, anti-P. Red-cell autoantibodies directed against blood-group-P antigen have until now only been detected, as polyclonal IgG antibodies, in paroxysmal nocturnal haemoglobinuria.