A patient develops hemolytic anemia after penicillin; what is the most appropriate description?

• A. The red blood cells are produced inappropriately
• B. An antigen-antibody reaction is destroying red blood cells
• C. An allergy to penicillin is destroying platelets
• D. Allergens are invading the bone marrow and interfering with red blood cell production

Answer: (B)

Drug-induced immune hemolytic anemia occurs when penicillin triggers the immune system to target red blood cells. The drug binds to the red cell surface (acting as a hapten) and forms a complex that antibodies recognize. These antibodies bind the complex and mark the red blood cells for destruction, typically by macrophages in the spleen or by complement, leading to hemolysis. So the scenario is best described as an antigen-antibody reaction destroying red blood cells. The other ideas point to problems with red cell production, platelet destruction, or marrow suppression, which are not how this mechanism operates.