This preparation reflects the blood count of a patient with Essential Thrombocythemia (ET, JAK2 positive). This disease is characterised by the excessive production of platelets, which also have abnormal morphology. In this case, the platelets are larger than normal (macrothrombocytes). Almost all platelets are affected.

One treatment for ET is the administration of hydroxyurea, a cytostatic that inhibits ribonucleoside reductase. This can cause macrocytosis and hypersegmentation. In this case, increased nuclear segmentation of both eosinophilic, basophilic and neutrophilic granulocytes is seen. This patient's platelet count was increased at 783*10^9/L.