Large and small platelets-(When) do they differ?

Platelets are most important in providing cellular hemostasis but also take part in inflammation and immune processes. Increased platelet size has been regarded as a feature describing a young and more reactive subpopulation until studies were published which questioned this concept. Moreover, changes of platelet size given by the mean platelet volume (MPV) were described for immune thrombocytopenia, cardiovascular disease, atherosclerosis, venous thromboembolism, chronic lung disease, sepsis, cancer-associated thrombosis, autoimmune disorders, and others. This review summarizes the literature on what is known about platelets with different size and describes controversies of studies with large and small platelets putting a focus on their thrombogenicity, age, and on the association of MPV with the mentioned diseases.