Impact of thrombotic thrombocytopenic purpura on leukemic children undergoing bone marrow transplantation

Thrombotic thrombocytopenic purpura (TTP) has emerged as one of the main tr ansplant-related complications over the last 15 years. The current study de fines the incidence and the risk factors for the occurrence of TTP in 131 c onsecutive leukemic children who were transplanted between January 1994 and December 1997 at four Italian pediatric centers. Patients with ALL (101), AML (21), MDS (9), underwent an HLA-identical sibling BMT (82) or an HLA-id entical unrelated BMT (49), receiving a conditioning regimen consisting of high-dose chemotherapy in 24 patients and of F-TBI combined with high-dose chemotherapy in 107 patients. The diagnosis of TTP was retrospectively eval uated on the basis of parallel criteria. TTP treatment varied according to the protocol of each treatment center. Twenty-eight of 131 patients (21.4%) developed TTP at a median of 46 days (range 21-80) after BMT. Multivariate analysis demonstrated that the risk of TTP was higher in patients who unde rwent unrelated BMT (P value = 0.02), Acute GVHD, stage of disease at BMT, conditioning with TBI, gender, age, did not appear to be associated with th e occurrence of TTP. As to the outcome, TTP resolved in 19 patients while i n nine it was the principal cause of death (32.1%). In patients with TTP, L DH peak value was the only statistically significant factor (P = 0.001) rel ated to severe TTP, In conclusion, our experience demonstrates that leukemi c children undergoing BMT, especially from an unrelated donor, should be ca refully assessed for TTP which appears to be a severe and relatively common transplant-related complication when strict diagnostic criteria are applie d.