European journal of haematology
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Congenital erythrocytosis can be classified as primary, when the defect is intrinsic to the RBC progenitors and independent of the serum erythropoietin (Epo) concentration, or secondary, when the erythrocytosis is the result of an upregulation of Epo production. Primary erythrocytosis is associated with mutations in the EPOR gene, secondary CE can de due to mutations that stabilize the hemoglobin in the oxygenated form or to mutations in the genes that control the transcriptional activation of the EPO gene - VHL, EGLN1, EPAS1. Chuvash polycythemia, caused by mutations in VHL gene, shares features of both primary and secondary erythrocytosis, with increased Epo production but also hypersensitivity of progenitors to Epo. ⋯ High-affinity hemoglobin variants are a very rare cause of secondary CE, but it seems likely that their incidence may be underestimated. Our experience shows that in erythrocytosis with a dominant inheritance and normal or inappropriate high Epo levels, the HBB and HBA genes should be the first to be studied. In spite of the seven genes known to be involved in CE, the majority of the cases have unknown etiology.