Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea.
Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by overproduction of myeloid white blood cells. Philadelphia chromosome is an essential finding for CML diagnosis. Generally, a clinical diagnosis of essential thrombocythemia (ET) can be established from isolated marked thrombocytosis in peripheral blood. However, Philadelphia chromosome-positivity or
Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with clonal hyperproliferation of myeloid cells in the bone marrow. Clinical findings in chronic-phase CML include fatigue, decreased appetite, and splenomegaly, and hematological findings include leukocytosis, thrombocytosis, neutrophilia, and decreased leukocyte alkaline phosphatase (LAP) scores .
Isolated thrombocytosis is assumed to be essential thrombocythemia (ET) rather than chronic-phase CML in most cases. According to the 2008 World Health Organization diagnostic criteria, a diagnosis of ET is routinely made, if platelet counts exceed 450×109/L with proliferation of megakaryocytes in the bone marrow and
We experienced a case of isolated thrombocytosis, initially suggestive of ET, positive for the Philadelphia chromosome and
A 21-year-old woman presented to the outpatient clinic with lower abdominal pain. Seven days before presentation, she had a ruptured corpus luteal cyst, which was detected on abdominal computed tomography (CT) at another clinic. Her initial platelet count was estimated to be 3,777×109/L at our clinic. Because thrombocytosis appeared to be secondary to bleeding, the patient's blood cell counts were only monitored during her clinical course. However, we decided to perform further evaluation because of thrombocytosis persisted for 2 weeks with no decrease in the platelet count. Her medical history was unremarkable, and she had no family history of hematologic disease or genetic disorders. Her vital signs were normal at admission. Except for mild lower abdominal tenderness, the patient had no other positive findings on physical examination. Complete blood count (CBC) revealed a hemoglobin level of 10.1 g/dL, hematocrit level of 30.7%, white blood cell (WBC) count of 10×109/µL (differential count: neutrophils 63%, lymphocytes 33%, eosinophils 1%, basophils 3%, and monocytes 0%), and platelet count of 3,294×109/L. A serum biochemistry panel showed the following: total protein, 7.2 g/dL; albumin, 3.9 g/dL; total bilirubin, 1.2 mg/dL; aspartate aminotransferase, 11 IU/L; alanine aminotransferase, 13 IU/L; blood urea nitrogen, 6 mg/dL; creatinine, 0.6 mg/dL; lactic dehydrogenase, 410 IU/L; and C-reactive protein, 2.0 mg/dL. A peripheral blood smear showed thrombocytosis. In addition, serum iron level was 73 µg/dL, total iron binding capacity was 267 µg/dL, and ferritin level was 206.5 ng/mL. The patient had an LAP score of 127 points, which was within the normal range. Abdominal and pelvic CT showed a small amount of hemoperitoneum resulting from the previous ruptured ovarian cyst. Bone marrow aspiration and biopsy revealed a high number of megakaryocytes, but no cells undergoing malignant transformation (Fig. 1, Fig. 2). A cytogenetic abnormality was detected with the karyotype 46,XX,t(9;22)(q34;q11.2) on bone marrow. We also observed a
Recently, a therapeutic advance in the treatment of CML was achieved with the advent of tyrosine kinase inhibitors for the
If severe thrombocytosis and hyperproliferation of megakaryocytes in the bone marrow occurs in the absence of splenomegaly, it is difficult to make a differential diagnosis between CML and ET without cytogenetic and molecular studies. Although the
A previous study showed mild basophilia and a Philadelphia chromosome in 1 of 121 patients with ET . This patient had a Philadelphia chromosome and isolated thrombocytosis that progressed to the accelerated phase, which is similar to the clinical course observed in a patient with CML. Patients with a Philadelphia chromosome and isolated thrombocytosis considered a variant of CML or an initial presentation of CML in the chronic phase were refractory to hydroxyurea, but showed improvement in symptoms and laboratory values after administration of imatinib .
Imatinib mesylate (Gleevec) is a
In conclusion, our case indicates that CML could not be completely excluded until the presence of the Philadelphia chromosome or
Thrombocytosis without obvious morphologic abnormalities of the white blood cells and erythrocytes in peripheral blood smear (Wright Giemsa stain, ×400).
Bone marrow core biopsy sample showing hypercellular bone marrow for age with expanded myelopoiesis and small megakaryocytes with decreased nuclear lobation (H&E stain, ×200).