SummaryBackgroundThe cause of idiopathic myelofibrosis (IM) originating from a haemopoietic stem cells with development of secondary marrow fibrosis is unknown. Increased production of platelet-derived growth factor by megakaryocytes causes amplified activity of fibroblasts. Thus, an analysis of changes in megakaryocyte population affecting fibrous expansion of the haemopoietic base is relevant.MethodsAnalysis and calculation of megakaryocytogram were carried out using bone marrow smears during routine examination of 12 patients with IM and 12 individuals without haematological disorders.ResultsHyperthrombocytemia prevailed in the peripheral blood of patients with IM. A significant increase was revealed in the content of megakaryoblasts (p<0.05), naked nuclei (p<0.01) both with diminished count of polychromatophilic megakaryocytes (p<0.05).Cells with picnotic nuclei surrounded with cytoplasm completely decomposed into platelets were distinguished as a separate population with a mean number of 21 ± 3.0%, out of which basophilic cells made up 9 ± 1.5% and polycromatophilic cells - 12 ± 1.9% (vs. 1 ± 0.4% in control) of the group investigated.Decrease in the megakaryocyte population with 4–8 nuclei lobules (p<0.001) at the expense of an increase in the megakaryocytes number with tight picnotic nuclei, naked nuclei and an increase in the number of 1-2 lobuled forms (p<0.05) were found.Contents of atypical micromegakaryocytes, giant hyperlobuled and dysplastic forms of megakaryocytes was increased.ConclusionThe changes revealed characterise differentiation disorder in the process of megakaryocytopoiesis. Megakaryocytes are subject to accelerated ageing and enhanced destruction with simultaneous prominent platelet production.