Erythrocytic ecdysis. An unusual morphologic finding in a case of sickle cell anemia with intercurrent cold-agglutinin syndrome.

Examination of peripheral blood smears from a patient with sickle cell disease during crisis associated with an upper respiratory tract infection, pneumonia, a positive Coombs test, and an elevated cold agglutinin titer revealed unique abnormalities associated with her erythrocytes, which have not been reported previously. In addition to the usual changes in peripheral blood occurring during crisis in sickle cell anemia, large numbers of free, filamentous forms that appeared to be derived from erythrocytes were present on repeated Wright's-stained smears. Erythrocytes were markedly distorted and had single and multiple surface protrusions that appeared to be antecedents of the free filamentous forms. Scanning electron microscopy confirmed the marked changes in the erythrocytes and revealed membrane alterations not apparent by use of the light microscope. It is suggested that the membrane stripping observed in this case was due to cold agglutinin--complement-mediated surface injury superimposed on the known abnormalities of the membranes of sickle erythrocytes.