Hemolytic anemia associated with multiple autoantibodies and low serum complement.

A 37 year old woman with extravascular hemolytic anemia had a positive Monospot test associated with positive antiglobulin and anticomplement Coombs' tests, cold agglutinins and warm autoantibodies. IgG-kappa (k) antibodies, which reacted with all panel red cells at 37 degrees C, were eluted from her circulating red cells. However, neither immunoglobulins nor C3 was detected after her serum was adsorbed with heterologous red cell stroma at 37 degrees C and eluted at the same temperature in glycine buffer. In contrast, IgM-kappa and IgM-lambda (lambda), IgG-3-kappa, IgG4-lambda, IgA-lambda and C3 were eluted at 37 degrees C from heterologous red cell stroma after adsorption with her serum at 0 degrees C. Thus, antibodies of several types, which were present in the patient's serum, reacted optimally with red cell antigens at low temperature. Cold-reactive IgG3-kappa antibodies, which also capable of interacting with red cells at 37 degrees C, probably accounted for the IgG-kappa antibodies eluted from the patient's circulating red cells. The patient's serum C4 titers were decreased, with low normal to moderately depressed C3 and low normal C5, indicating that the anti-red cell IgM and/or IgG3-kappa antibodies probably fixed complement. A localized cold stress test resulted in a transient increase in plasma hemoglobin and a decrease in serum C3 titer. These findings, and the beneficial clinical response obtained with small doses of prednisone, suggest that both the cold-reactive antibodies and the IgG-kappa on circulating red cells were pathophysiologically significant. This is the first report of a patient with multiple red cell autoantibodies in whom serum complement component titers were determined in conjunction with characterization of the anti-red cell immunoglobulins. Subclinical infectious mononucleosis may have preceded the prolonged hemolytic episode. Clinical evidence of systemic lupus erythematosus has not appeared.