BU exposure was significantly associated with aGvHD, TRT and hemorrhagic cystitis and was further analyzed together with genotypes/diplotypes in a multivariate model in which both variables remained significant predictors of respective outcomes (GSTA1, p = 0.003, GSTM1, p = 0.005, Css p ≤ 0.05, (Table 4b). The gene discussed is GSTM1; the disease is hemorrhagic cystitis.