Immune hemolytic anemia due to diclofenac

A 37-year-old male presented with severe anemia, mild jaundice, and hemoglobinuria during his second course of diclofenac for gout. The peripheral blood showed microspherocytes and nucleated red blood cells (RBCs). The reticulocyte count was 21 percent and haptoglobin was < 0.1 g/L. A presumptive diagnosis of diclofenac-induced immune hemolysis was made and blood, urine, and drug samples were referred for investigation. Direct antiglobulin testing showed the RBCs to be coated with IgG1, IgG4, and C3d, but an eluate only yielded weakly reacting IgG antibodies. In tests for drug-dependent antibodies, group O, R1R2 red cells were incubated with the patient's serum that had been mixed with either urine (which contained diclofenac metabolites) or diclofenac solution and then tested by an antiglobulin method. Strongly positive reactions with anti-IgG occurred in the tests using urine but only weak reactions in those tests employing diclofenac solution. All controls gave negative results. These findings support the role of diclofenac in causing hemolysis and the importance of employing urine as a source of drug metabolites. The findings also showed that an immune complex mechanism predominated and that the eluted IgG (detectable independently of the presence of the drug or its metabolites) confirmed a minor autoimmune component. Diclofenac was stopped and treatment with prednisolone and folic acid instituted; this resulted in complete recovery.