Platelet volume is the size of the platelets, the normal range is 7-11 fL, below 7 fL is low platelet volume. In clinical practice, the most common cause of low platelet volume is a bone marrow hematopoietic disorder, such as aplastic anemia, in which small platelets are formed due to damage to hematopoietic stem cells, failure of the hematopoietic function of the bone marrow, and decreased ability of megakaryocytes to divide and form platelets. At the same time, the number of platelets is reduced. In addition, in about half of the patients with leukemia, the proliferation of normal cells is affected by the proliferation of leukemic cells in the bone marrow, and megakaryocytes are then unable to divide normally into effective platelets, but instead divide to form many small-sized platelets, which eventually leads to a decrease in platelet volume. In addition, if platelet bodies become smaller as the number of platelets decreases, this is one of the signs of severe bone marrow hematopoietic failure.