Platelet distribution width is an indicator of the dispersion of platelet volume size in peripheral blood, that is, whether the size of platelets in peripheral blood is homogeneous. A low platelet distribution width indicates that the platelets in peripheral blood are uniform in size and do not vary greatly in size. In clinical practice, the most common diseases with low platelet distribution width are various bone marrow hematopoietic disorders, the most common of which is aplastic anemia. In aplastic anemia, due to bone marrow hematopoietic failure, the ability of megakaryocytes to produce platelets is reduced, and the platelets produced are small in size, resulting in a reduced platelet volume distribution width. The platelet volume distribution width is also reduced due to bone marrow suppression and poor bone marrow hematopoiesis in leukemia patients after chemotherapy.