Masked Polycythemia Vera and Iron Deficiency in a Fertile-Age Woman

Polycythemia vera (PV) is a myeloproliferative disorder that leads to increased red blood cell (RBC) mass. The V617F activating mutation for Janus kinase 2 (JAK2) is a classic finding in PV, but it is not exclusive to this condition. The radionuclide assay is an accurate method for accessing RBC, but hemoglobin (Hb) and hematocrit (Htc) values are frequently the first abnormal markers reported in a routine blood count and the basis for further investigation. Diagnostic criteria for PV were recently updated to include lower thresholds for Hb and Htc, increasing diagnostic sensitivity. However, it has been reported that a subset of patients does not meet these thresholds, besides having an active masked disease. We are presenting a case of a fertile-age woman with menometrorrhagia, whose blood loss and consequent iron depletion worked as a limiting factor for Hb and Htc increase, delaying the proper diagnosis. Splenomegaly, iron deficiency markers, and low erythropoietin supported PV investigation. The correction of iron depletion led to the unveiling of covert erythrocytosis. Concomitant hemoglobinopathies and secondary causes for erythrocytosis were excluded. The diagnosis was confirmed with polymerase chain reaction (PCR) for V617F-JAK2 mutation and bone marrow biopsy. As this case highlights, despite not meeting diagnostic criteria at presentation, masked PV exhibited clinical, laboratory, and imaging features of active symptomatic disease. For that, a higher level of suspicion must be held for fertile-age women who present with normal Hb and Htc levels and significant iron depletion, in the presence of low serum erythropoietin or splenomegaly.