THROMBOCYTOSIS IN PATIENTS WITH ACUTE PROMYELOCYTIC LEUKEMIA DURING ALL-TRANS-RETINOIC ACID TREATMENT

In 26 acute promyelocytic leukaemia (APL) patients treated with all-tr ans retinoic acid (ATRA), 23% had platelet counts between 459 and 800 x 10(9)/l 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)/l during ATRA therapy wh o were treated with recombinant interferon alpha. In both cases ATRA d oses were not modified, no complications secondary to thrombocytosis w ere seen, and they subsequently achieved complete remission. It is sug gested that IL-6 may play an important role in the pathogenesis of the thrombocytosis induced by ATRA. To our knowledge, this is the first r eport of thrombocytosis occurring during ATRA treatment.