Myeloproliferative neoplasm, more formally known as myeloproliferative neoplasm (MPN), is a clonal, chronic, proliferative disease of the bone marrow that originates from the hematopoietic stem cells and is acquired. It is characterized by an unrestricted clonal proliferation of one or more lines of granulocytes, erythrocytes and megakaryocytes in the bone marrow, and a significant increase in the peripheral blood count of white blood cells, red blood cells and platelets. It is called clonal hyperplasia because most of the hyperplastic blood cells carry abnormal genetic mutations that are not present in normal blood cells, such as JAK2 gene mutation, CALR mutation, etc. This type of disease is most often seen in people over 60 years of age and contains five diseases, including true erythrocytosis, primary thrombocytosis, chronic granulocytic leukemia, chronic granulocytic leukemia, and primary myelofibrosis.