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Kim, Lee, Choi, Kang, Jang, Moon, and Park: Primary Myelofibrosis with MPL S505N Mutation: The First Case Reported in Korea

Abstract

MPL mutation is an important molecular marker in myeloproliferative neoplasms (MPN). Although MPL W515 is a hot spot for missense mutations in MPN, MPL S505 mutations have been reported in both familial and non-familial MPN. A 72-year-old male visited the hospital, complaining mainly of dizziness and epistaxis. Leukocytosis, anemia, thrombocytopenia, tear drop cells, nucleated RBCs, and myeloblasts were observed in both complete blood cell counts and peripheral blood smears. Bone marrow aspiration failed due to dilution with peripheral blood. BM biopsy indicated hypercellular marrow, megakaryocytic proliferation with atypia, and grade 3 reticulin fibrosis. Conventional cytogenetics results were as follows: 46,XY,del(13)(q12q22)[19]/46,XY[1]. Molecular studies did not detect JAK2 V617F, BCR/ABL translocation, JAK2 exon 12, and CALR exon 9 mutations. The MPL S505N mutation was verified by colony PCR and Sanger sequencing following gene cloning. Based on the above findings, a diagnosis of overt primary myelofibrosis (PMF) was indicated. Mutation studies of buccal and T cells were not conducted. Further, family members were not subjected to mutation studies. Therefore, we were unable to determine whether this mutation was familial or non-familial. Six months after the first visit to the hospital, the patient died due to pneumonia and sepsis. Thrombotic symptoms or major bleeding events did not develop during the survival period following diagnosis of PMF. To the best of our knowledge, this may be the first reported case of PMF with the MPL S505N mutation in Korea.

Figures and Tables

Fig. 1

Peripheral blood and bone marrow section findings. (A) Wright-Giemsa-stained peripheral blood smear showing a myeloblast with nucleated RBC and tear drop cells (×400). (B) H&E-stained bone marrow section showing hypercellularity with increased number of megakaryocytes (×400). (C) CD61 immunohistochemical staining of a bone marrow section showing an increased number of atypical megakaryocytes that form dense clusters (×400). (D) Reticulin stained bone marrow section showing a diffuse increase in reticulin, as well as focal bundles of reticulin and numerous distorted megakaryocytes (×400).

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Fig. 2

Chromatograms of direct sequencing (A) and colony PCR-sequencing following gene cloning (B). A minor adenine peak was observed in the direct sequencing chromatogram. The MPL S505N (NM_005373.2:c.1514G>A, rs121913614) mutation was observed in the colony PCR-sequencing chromatogram.

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