A 63-year-old woman experiences a burning sensation in her hands and feet. Two months ago, she had an episode of swelling with tenderness in the right leg, followed by dyspnea and right-sided chest pain. On physical examination, the spleen and liver now appear to be enlarged. CBC shows hemoglobin, 13.3 g/dL; hematocrit, 40.1%; MCV, 91 mm3; platelet count, 657,000/mm3; and WBC count, 17,400/mm3. The peripheral blood smear shows abnormally large platelets. Which of the following is the most likely diagnosis?
Essential thrombocytosis is a myeloproliferative disorder. As with all myeloproliferative diseases, the transformation occurs in a myeloid stem cell. In this form of myeloproliferative disease, the dominant cell type affected is the megakaryocyte, and there is thrombocytosis. Other myeloproliferative disorders, such as chronic myelogenous leukemia, myelofibrosis, and polycythemia vera, also can be accompanied by an increased platelet count. The diagnosis of essential thrombocytosis can be made after other causes of reactive thrombocytosis are excluded, and if the bone marrow examination shows increased megakaryocytes with no evidence of leukemia. The throbbing, burning pain in the extremities is caused by platelet aggregates that occlude small arterioles. The major manifestation of this disease is thrombotic or hemorrhagic crises. The swelling in this patient's leg represents phlebothrombosis, followed by pulmonary embolism with infarction. The peripheral blood WBC count would be high in acute myelogenous leukemia, without thrombocytosis.
Acute myelogenous leukemia
Chronic myelogenous leukemia
Essential thrombocytosis
Myelofibrosis with myeloid metaplasia
Blood