RESUMO
Cyclophosphamide, a prodrug requiring metabolic activation by cytochrome P450 (CYP) enzymes, is used widely for proliferative lupus nephritis and various CYP isoenzymes have been demonstrated to be involved in the bioactivation of cyclophosphamide in humans, including CYP2A6, 2B6, 2C19, 2C9, 3A4, and 3A5. The response or adverse event after intravenous cyclophosphamide pulse therapy in lupus nephritis patient seems to be different for each individual and genetic polymorphism of CYP may explain the difference. Generally, wild types of CYP seem to be more active in the activation of cyclophosphamide than variant types of CYP. Here, we report a case of lupus nephritis with a genotype of CYP2A6*1B who suffered from severe leukopenia after intravenous cyclophosphamide pulse therapy.