Simultaneous drug-induced immune hemolytic anemia (DIIHA) caused by multiple drugs is rare. We report a case of a patient who developed DIIHA caused by 2 drugs. The patient's serum exhibited agglutination of ceftizoxime- or sulbactam-coated red blood cells (RBCs; via a drug-adsorption mechanism) and of uncoated RBCs in the presence of sulbactam (via an immune-complex mechanism). Although ceftizoxime is known to exhibit a positive reaction by an immune-complex method with or without reactivity with drug-coated RBCs, this patient's antibodies were reactive only against drug-coated RBCs. On the other hand, sulbactam, which is known to cause hemolytic anemia by nonimmunologic protein adsorption, exhibited positive reactions in tests with both drug-coated RBCs and in the presence of sulbactam. This is the first report of DIIHA due to a sulbactam-cefoperazone combination and the fourth report of DIIHA due to ceftizoxime. Owing to the patient's complicated laboratory results, DIIHA was suspected only at a late stage. We propose that for the prompt diagnosis of DIIHA, tests for all possible causative drugs should be conducted by 2 methods.
Anemia, Hemolytic/chemically induced/*diagnosis/immunology ; Anti-Bacterial Agents/*adverse effects ; Cefoperazone/*adverse effects ; Ceftizoxime/*adverse effects ; Erythrocytes/chemistry/metabolism ; Female ; Humans ; Middle Aged ; Sulbactam/*adverse effects