Thrombotic thrombocytopenic purpura (
TTP) has emerged as one of the main transplant-related complications over the last 15 years. The current study defines the incidence and the risk factors for the occurrence of
TTP in 131 consecutive 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-identical 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 evaluated 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 underwent 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 the occurrence of
TTP. As to the outcome,
TTP resolved in 19 patients while in nine it was the principal cause of death (32.1%). In patients with
TTP, LDH peak value was the only statistically significant factor (P = 0.001) related to severe
TTP. In conclusion, our experience demonstrates that leukemic children undergoing BMT, especially from an unrelated donor, should be carefully assessed for
TTP which appears to be a severe and relatively common transplant-related complication when strict diagnostic criteria are applied.