Haematopoietic progenitors in essential thrombocythaemia.

Colony formation by haematopoietic progenitors from the bone marrow and blood of 4 patients with essential thrombocythaemia was studied in vitro using the methyl cellulose assay. 3 patients had clearly elevated numbers of BFU-E in bone marrow. 1 patient also had markedly increased numbers of CFU-E and CFU-GM, whereas the other patients had only marginally increased or normal numbers of these progenitors in the marrow. 3 patients showed markedly increased numbers of all progenitors in peripheral blood. All 4 patients showed spontaneous erythroid colony formation by progenitors from the bone marrow and 2 had spontaneous colony formation by progenitors from the blood. We conclude that essential thrombocythaemia shows abnormal colony formation in line with other myeloproliferative syndromes.