The Lewis system and secretor status in autoimmune hemolytic anemia complicating infectious mononucleosis.

Two patients with acute infectious mononucleosis and associated immune hemolysis were found to be Le(a-b-). One of them had anti-Leb antibodies during the acute phase of the disease, which disappeared during convalescence. Two other patients with previous infectious mononucleosis and hemolysis were found to be Le(a-b-) and Le(a+b-) respectively. Of the four patients, three were nonsecretors and the fourth likely to be so. The Lewis status of these four patients varies significantly from that of other patients with uncomplicated infectious mononucleosis and from the known distribution of the Lewis type in the Caucasian population. The findings suggest that the Lewis status of the patient is important in the development of hemolysis in infectious mononucleosis.