Von Willebrand factor--cleaving protease activity in congenital thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is characterized by microangiopathic haemolytic anaemia (MAHA), thrombocytopenia, fluctuating neurological impairment, renal dysfunction and fever. Both acquired and congenital forms are recognized. Recurrent episodes, which may be predictable (occurring every 21-28 d), are seen in congenital disease and may be treated by infusion with fresh-frozen plasma (FFP). Congenital TTP has recently been associated with deficiency of a novel von Willebrand factor (VWF)-cleaving protease. To investigate whether residual protease activity dictates clinical manifestations, we determined protease activity in three patients with congenital TTP of varying severity. Intrinsic VWF-cleaving protease activity of a range of plasma-derived products was also assessed as one patient had been successfully maintained for many years, initially using an intermediate-purity factor VIII concentrate (Kryobulin) and then cryoprecipitate. All three patients had a severe absolute deficiency of VWF-cleaving protease activity (< 3%) up to 5 months after clinical symptoms. Three relatives were also found to have a mild reduction in protease activity (25-50%). Nevertheless, the intrinsic VWF-cleaving protease activity of plasma-derived products correlated with their clinical efficacy: significant (100%) protease activity was found in FFP, cryosupernatant, solvent-detergent-treated plasma, cryoprecipitate and Kryobulin. Two clinically ineffective factor VIII products (Fahndi and Haemate P) possessed only low protease activity (6.25% and 12.5% respectively). Although this suggests that VWF-cleaving protease activity is central to the pathogenesis of congenital TTP, either small differences in protease activity below 3% or hitherto unknown factors have a profound influence on clinical phenotype. The possible use of factor VIII concentrates in the treatment of this condition also warrants further investigation.

Identification of the t(15;17) in AML FAB types other than M3: evaluation of the role of molecular screening for the PML/RARalpha rearrangement in newly diagnosed AML. The Medical Research Council (MRC) Adult Leukaemia Working Party.

Acute promyelocytic leukaemia (APL) is characterized by the t(15;17) leading to the formation of PML-RARalpha and RARalpha-PML fusion genes; this rearrangement has been considered both diagnostic for, and restricted to, this subtype of acute myeloid leukaemia (AML FAB M3). We describe two cases of AML with the t(15;17) associated with a PML/RARalpha rearrangement which lacked typical APL morphology, classified as FAB M1 and M2 respectively. In both cases morphological review revealed small populations of cells which exhibited some features associated with APL. In the case classified as M1, PML immunofluorescence studies revealed the classic microparticulate nuclear staining pattern as observed in typical cases of APL with the t(15;17). Similarly, blasts from this case were found to be sensitive to ATRA in vitro as determined by NBT reduction test and by normalization of the PML nuclear body staining pattern. To determine the frequency of PML/RARalpha rearrangements in FAB subtypes other than M3, 530 patients from the MRC AML trials were screened using nested RT-PCR. Only one individual, initially classified as M5 with a normal karyotype, was found to have a PML/RARalpha rearrangement. The diagnosis was revised to M3 variant on subsequent morphological review. In conclusion, this study demonstrates that, in rare cases, the t(15;17) is not restricted to patients with M3 morphology as defined by current FAB criteria. Therefore, although we consider cytogenetic analysis of newly diagnosed cases of AML to be mandatory, our data suggests that routine molecular screening for PML/RARalpha rearrangements is not justified and should be reserved for those cases displaying features which may be suspicious of APL even if such cells comprise only a minority of the total population.

Idarubicin, high-dose cytarabine, and etoposide for induction of remission in acute leukemia.

Between 1990 and 1944, 52 newly diagnosed patients with primary (n = 47) or therapy-related (n = 5) acute myeloid leukemia (AML) under the age of 55 years received an induction chemotherapy protocol (designated BF12) consisting of idarubicin ([IDA] 5 mg/m2), high-dose cytarabine ([HD-Ara-C] 2 mg/m2 per 12 hours, 3-hour infusion), and etoposide ([VP-16] 100 mg/m2, 1-hour infusion) on each of 5 consecutive days. Thirty-seven of 51 assessable patients (72.5%), including all five patients with therapy-related AML, attained remission with one cycle. The overall remission rate was 78.4%. Total therapy of AML, with BF12 followed by two courses of consolidation therapy and allogeneic or unpurged autologous bone marrow transplantation (BMT) in first remission, has resulted in actuarial 3-year survival of 49.9% of consecutive unselected patients with newly diagnosed primary AML (minimum follow-up period, 1 year). Twenty-five patients have received BF12 for relapsed acute leukemia, including 13 relapsing after BMT. Five patients died of toxicity and were not assessable for response. Of the remaining 20 patients, five were refractory, two attained partial remissions, and 13 (65%) achieved complete remission (CR). Four of the 13 patients relapsing after BMT died of toxicity, four were refractory, and five of nine assessable patients (56%) attained CR. We conclude that the combination IDA/HD-Ara-C/VP-16 is highly effective in the treatment of newly diagnosed AML and relapsed acute leukemia.