Extensive bilateral pulmonary embolism revealing iron deficiency-masked JAK2-positive polycythemia vera: A case report.

Polycythemia vera is a BCR-ABL1-negative myeloproliferative neoplasm associated with increased thrombotic risk. Pulmonary embolism as the initial manifestation of iron deficiency-masked polycythemia vera is uncommon and may be difficult to recognize when hemoglobin and hematocrit are not overtly elevated. We report the case of a 67-year-old postmenopausal woman with no identifiable thromboembolic risk factors who presented with acute dyspnea. Computed tomography pulmonary angiography showed extensive bilateral pulmonary embolism involving proximal and distal pulmonary arterial branches, with a right ventricular-to-left ventricular diameter ratio greater than 1, consistent with right ventricular strain. Transthoracic echocardiography confirmed right ventricular dilation and systolic dysfunction, with a tricuspid annular plane systolic excursion of 9 mm. No deep venous thrombosis was identified. The association of unprovoked pulmonary embolism, right ventricular dysfunction, and subtle hematologic abnormalities prompted evaluation for an underlying myeloproliferative neoplasm. Laboratory tests showed an elevated red blood cell count with high-normal hemoglobin (15 g/dL) and hematocrit (45.9%), marked microcytosis with a mean corpuscular volume of 66.5 fL, and low mean corpuscular hemoglobin of 21.7 pg. Further workup revealed low ferritin, low transferrin saturation, and subnormal serum erythropoietin. Molecular testing identified a JAK2 V617F mutation, and bone marrow biopsy showed hypercellular marrow with trilineage proliferation. The patient received therapeutic anticoagulation, low-dose aspirin, and hydroxyurea. This case highlights the role of multimodal imaging in diagnosis and risk stratification, and the need to consider masked polycythemia vera in unprovoked pulmonary embolism with unexplained microcytosis and elevated red blood cell count.