Clinical and immunologic features of transient cold agglutinin hemolytic anemia

Atypical pneumonitis, often induced by infection with Mycoplasma pneumoniae, is frequently associated with elevated cold agglutinin titers but only rarely with significant hemolytic anemia. An example and documentation of the clinical and immunologic course of such transient cold agglutinin hemolytic anemia is presented, and the immunochemical characteristics of cold agglutinins in this syndrome are assessed in regard to their biologic implications and diagnostic significance. Transient cold agglutinins, such as observed in this case, commonly appear to be of a restricted polyclonal character and as first demonstrated in this case may possess structural determinants usually considered unique for monoclonal cold agglutinins. Although the immunopathogenetic mechanisms and certain clinical manifestations of the various forms of cold agglutinin hemolytic anemia appear similar, the immunogenic basis of cold agglutinin production and the molecular structure of transient cold agglutinins are quite distinctive and provide reasonably reliable guidelines for the differential diagnosis of the cold agglutinin syndromes and for consideration of appropriate clinical management.