[Chronic myeloid leukemia beginning as thrombocythemia. Analysis of 5 cases].

The clinico-haematological and evolutive features of five patients with Ph'-positive chronic myelogenous leukaemia (CML) whose initial profile suggested the diagnosis of essential thrombocythaemia (ET) were analysed. The patients were women with severe thrombocytosis (greater than or equal to 1000 x 10(9)/L) and moderate leucocytosis (less than 25 x 10(9)/L), and only two of them had splenomegaly. Increased basophil count in peripheral blood was present in all cases, and peripheral myelocytosis was seen in three. The molecular analysis showed rearrangement of the BCR gene in the three patients on which it was performed. Increasing leucocyte count was seen in the three patients with extended follow-up, this reaching values in accordance with CML. Finally, the three patients who died suffered a blastic crisis. The analysis of this series, along with others reported in the literature, suggests that such cases correspond to atypical forms of CML rather than actual TE patients.