title: BCR-ABL1- positive chronic myeloid leukemia with erythrocytosis presenting as polycythemia vera: a case report.
abstract: BACKGROUND
  The World Health Organization classification of chronic myeloproliferative disease encompasses eight entities of bone marrow neoplasms, among them Breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1-positive chronic myeloid leukemia and polycythemia vera. Polycythemia vera requires, in the majority of cases (95%), the negativity of Breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 rearrangement and the presence of the Janus kinase 2 mutation. We report a case of erythrocytosis as the primary manifestation of a chronic myeloid leukemia, with the presence of the Philadelphia chromosome and the Breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 fusion gene, and in the absence of any Janus kinase 2 mutation.
  
  
  METHODS
  A 68-year-old Caucasian woman, with a history of cigarette consumption and obstructive sleep apnoea syndrome (undergoing continuous positive airway pressure treatment) had presented to our institution with fatigue and a hemoglobin level of 18.6g/L, with slight leukocytosis at 16G/L, and no other anomalies on her complete blood cell count. Examination of her arterial blood gases found only a slight hypoxemia; erythropoietin and ferritin levels were very low and could not explain a secondary erythrocytosis. Further analyses revealed the absence of any Janus kinase 2 mutation, thus excluding polycythemia vera. Taken together with a high vitamin B12 level, we conducted a Breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 gene analysis and bone marrow cytogenetic analysis, both of which returned positive, leading to the diagnosis of chronic myeloid leukemia.
  
  
  CONCLUSIONS
  To date, this case is the first description of a Breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1-positive chronic myeloid leukemia, presenting with erythrocytosis as the initial manifestation, and mimicking a Janus kinase 2 V617F-negative polycythemia vera. Her impressive response to imatinib therapy underscores the importance of not missing this diagnosis.
authors.affiliation: Hôpital Cantonal Fribourg, Chemin des Pensionnats 2, 1708, Fribourg, Switzerland. Mihaela.Precup@h-fr.ch.
authors.forename: Mihaela I Precup
authors.initials: MI
authors.lastname: Cornea
authors.affiliation: Hôpital Cantonal Fribourg, Chemin des Pensionnats 2, 1708, Fribourg, Switzerland. Emmanuel.Levrat@h-fr.ch.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Levrat
authors.affiliation: Hôpital Cantonal Fribourg, Chemin des Pensionnats 2, 1708, Fribourg, Switzerland. Paul.Pugin@h-fr.ch.
authors.forename: Paul
authors.initials: P
authors.lastname: Pugin
authors.affiliation: Hôpital Cantonal Fribourg, Chemin des Pensionnats 2, 1708, Fribourg, Switzerland. Daniel.Betticher@h-fr.ch.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Betticher
mesh_terms: D000368:Aged; D002908:Chronic Disease; D003937:Diagnosis, Differential; D005260:Female; D016044:Fusion Proteins, bcr-abl; D006801:Humans; D000068877:Imatinib Mesylate / Q000627:therapeutic use; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000150:complications* / Q000188:drug therapy; D011086:Polycythemia / Q000150:complications* / Q000188:drug therapy; D011087:Polycythemia Vera / Q000150:complications* / Q000188:drug therapy; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use
chemical_list: C581634:BCR-ABL1 fusion protein, human; D047428:Protein Kinase Inhibitors; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl