In 26 acute promyelocytic leukaemia (APL) patients treated with all-trans retinoic acid (ATRA), 23% had platelet counts between 459 and 800 x 10(9)/I during treatment. These values, observed between days 28 and 45 of ATRA treatment, were transient and asymptomatic. We report two APL cases with platelet counts > 1000 x 10(9)/I during ATRA therapy who were treated with recombinant interferon alpha. In both cases ATRA doses were not modified, no complications secondary to thrombocytosis were seen, and they subsequently achieved complete remission. It is suggested that IL-6 may play an important role in the pathogenesis of the thrombocytosis induced by ATRA. To our knowledge, this is the first report of thrombocytosis occurring during ATRA treatment.

We are now working on a distributed parameter model with the aim of estimating erythroid cell maturation time, and non-haem and haem iron pools in marrow from ferrokinetic data only (Barosi et al, 1977). We believe that the diagnostic power of ferrokinetic studies in clinical evaluation of erythroid disorders can be augmented by refining the model describing iron kinetics.

We performed Southern-blot analysis of the p53 gene in 41 consecutive patients with typical chronic myelocytic leukemia (CML). In two of them, we were able to study cells during both the chronic and the accelerated phases. Only one of the 29 chronic-phase samples had rearrangement of the p53 gene, whereas three of the nine accelerated-phase samples and one of the five patients in blast crisis exhibited rearrangements. Gene deletion was observed in two patients, one in accelerated phase and the other in blast crisis. One patient with a nonrearranged p53 gene in chronic phase showed rearrangement after progression to the accelerated phase. On the other hand, one patient in accelerated phase exhibited rearrangements which disappeared after reversion to chronic phase with successful treatment. Our findings support the opinion that alterations of the p53 gene may play an important role in CML evolution.

Seven patients with acute promyelocytic leukemia (APL) were treated with all-trans retinoic acid (ATRA). Five (71.4%) achieved complete remission (CR). Most side effects were transient and well tolerated. Hyperleukocytosis was the major adverse effect. These observations confirm the efficacy of ATRA for inducing CR in APL.

Cytogenetic and molecular techniques were performed on samples obtained from 29 patients with chronic myelocytic leukemia (CML); 27 were in the chronic phase and two were in blast crisis. A further five cases were also analyzed, two with atypical CML (aCML), one with chronic neutrophilic leukemia (CNL), and two with juvenile CML (JCML). Most of the cases with typical CML were Philadelphia chromosome (Ph) positive and had a rearrangement within the major breakpoint cluster region (M-bcr). One of these cases was shown to be Ph positive but showed no rearrangement within the M-bcr. Two cases with clinical features typical of CML were Ph negative. One of these showed a rearrangement within the M-bcr, but no rearrangement was demonstrated in the other. Both patients in blast crisis were Ph positive and M-bcr positive. One showed a second Ph. Patients with aCML were Ph negative and had no M-bcr rearrangement. A polymorphism within the M-bcr was found with BglII in one case. No Ph chromosome or M-bcr rearrangement was found in CNL or JCML. These data support the molecular heterogeneity reported in CML.