Platelet morphology

Abstract

BackgroundThe examination of a peripheral blood smear is mandatory in case of unexplained thrombocytopenia or thrombocytosis. First, the number of platelets should be estimated in order to confirm the platelet count determined by the haematology analyser, and to rule out causes of spuriously low or elevated platelet counts. Second, the size and morphological features of the platelets, which may provide information on the underlying cause of the low or enhanced platelet count, have to be assessed.ContentThis review summarizes the physiological and pathological features of platelet size and morphology, circulating megakaryocytes, micromegakaryocytes and megakaryoblasts, and provides an overview of current guidelines on the reporting of platelet morphology.SummaryIn the diagnostic work-up of a patient with thrombocytopenia, the size of the platelets is of diagnostic relevance. Thrombocytopenia with small platelets is suggestive of a defect in platelet production, whereas the presence of large platelets is more likely to be associated with enhanced platelet turnover or hereditary thrombocytopenias. Morphological platelet abnormalities may affect the granulation and the shape and are frequently associated with abnormalities of platelet size. Platelet anomalies can be found in various haematologic disorders, such as myelodysplastic syndromes, myeloproliferative neoplasms, acute megakaryoblastic leukaemia or hereditary thrombocytopenias.

Platelets, Bacterial Adhesins and the Pneumococcus

“…Platelets are anucleated, discoid shaped cells of the blood with a size of 2–4 µm in diameter [ 1 ]. Platelets are derived from megakaryocyte (MK) shedding in the bone marrow and the lungs [ 2 , 3 ].…”

Morphometric and Nanomechanical Features of Platelets from Women with Early Pregnancy Loss Provide New Evidence of the Impact of Inherited Thrombophilia

“…The first event that takes place is related to a change in cells' shape from discoid to spherical, followed by prominent cell-cell interactions and clustering through extending actin-rich philopodia; in the final phase, flattening and spreading of cells on the damaged surface is observed, which results in the sealing of the impaired vessels. More precisely, five stages of spreading and activation of platelets can be distinguished: (1) round or discoid without pseudopodia; (2) dendritic with early pseudopodia but without flattening; (3) spread-dendritic with intermediate pseudopodia (one or more flattened pseudopodia) without spreading of the cell body; (4) initial spreading with late pseudopodia; (5) fully spread without distinct pseudopodia [3,4]. Abnormalities in platelets size and shape, as well as in the activation process, are related not only to impaired haemostasis but also to various pathologies and inherited platelet disorders [5,6].…”

“…More precisely, five stages of spreading and activation of platelets can be distinguished: (1) round or discoid without pseudopodia; (2) dendritic with early pseudopodia but without flattening; (3) spread-dendritic with intermediate pseudopodia (one or more flattened pseudopodia) without spreading of the cell body; (4) initial spreading with late pseudopodia; (5) fully spread without distinct pseudopodia [3,4]. Abnormalities in platelets size and shape, as well as in the activation process, are related not only to impaired haemostasis but also to various pathologies and inherited platelet disorders [5,6]. Platelets are also involved in metastasis, various inflammatory processes, innate and adaptive immune defences, and embryonic development [7].…”

Up-to date platelet testing

“…When platelet dysfunction is assumed, light microscopy for the assessment of platelet size and morphology is an indispensable tool to narrow down the possible causes. Robier [4] presents an up-to-date overview including illustrative microscopic examples of preanalytical artefacts and typical clinical conditions. Light microscopy attained an even larger importance in the last years since for many genetic disorders of platelet function the causative genes have been identified and a detailed microscopic analysis including megakaryocytes, micromegakaryocytes and megakaryoblasts morphology will aid in the straightforward selection of the possible gene mutations for sequencing analysis.…”

“…However, differences between these standards can infringe patients' safety in particular when physiological observations such as a few giant platelets or dysplastic platelets in an otherwise normal blood count are mistaken for a pathological condition. The article [4] describes in detail the caveats of these different reporting standards and gives recommendations for the uniform reporting of qualitative platelet abnormalities.…”