Thrombocytopenia as presenting symptom of preleukaemia in 3 patients.

3 patients with preleukaemia (idiopathic acquired myelodysplasia) presenting with isolated peripheral thrombocytopenia and an increased number of megakaryocytes are described. The diagnosis of preleukaemia, however, was strongly suspected on bone marrow morphology, revealing an abnormal megakaryocytic series. Megakaryoblasts with characteristic nuclei and basophilic pseudopodes, and immature megakaryocytes were frequent. These last cells had 1 or 2 nuclei and a basophilic poorly granulated cytoplasm, often containing large vacuoles, corresponding to dilated interconnecting demarcation membranes in electron microscopy. Megakaryocytes were not considered able to produce a normal amount of platelets, explaining the peripheral thrombocytopenia; platelet survival (51Cr) was indeed too long for ITP. Cytogenetic analysis confirmed the diagnosis of an abnormal haematopoietic clone. Ferrokinetics, in vitro agar cultures, bone marrow biopsy and platelet function tests were helpful additional examinations for establishing the correct diagnosis. It is important to differentiate preleukaemia from ITP. Prognosis is totally different and the treatment is not only ineffective in the great majority of the preleukaemic patients, but may be hazardous.