P1012: A NUMBER OF CONGENITAL ERYTHROCYTOSIS ARE MULTIGENIC

Abstract

Background: Imbalance in erythropoiesis and oxygen homeostasis could lead to the onset of Erythrocytosis, a clinical condition characterized by persistently raised hemoglobin (Hb) and hematocrit (Ht) levels. Nowadays, a high number of patients are classified as “Idiopathic Erythrocytosis” (IE) meaning that it is not possible to identify the cause of hematocrit increase. Recently, HFE mutations has been found to be often present in idiopathic erythrocytic patients. The HFE mutations could facilitate the increase in red cell mass, and this indicates the possible involvement of Iron Metabolism in causes of IE. Aims: To identify the possible mutations of IE patients using our gene panel for Next Generation Sequencing (NGS). Methods: In 118 patients with IE, regularly followed in our surgery, we used a gene panel for NGS composed by fifteen genes: JAK2, EGLN1 (PHD2), EPO-R, FTL, FTH, ASXL1, HFE, HFE2, TFR2, HAMP, SLC40A1, SLC11A2, VHL, BPMG, EPAS1 (HIF-2α). We analyzed all the exons parts of these genes. The approach used for the library preparation was a multiplexing PCR and data were analyzed by bioinformatics tools. In all patients, the mutations found were confirmed with Sanger Sequencing. Results: In 78 out of the 118 patients (66%) evaluated, we found one 1 mutated gene in 55 patients (7 EGLN1, 1 VHL, 34 HFE, 6 TFR2, 3 JAK2 and 4 EPO-R), 2 mutated genes in 18 patients (1 EGLN1/JAK2, 4 EGLN1/HFE, 2 EPAS1/HFE, 1 EPAS1/JAK2, 1 EPAS1/EGLN1, 2 EPO-R/HFE, 2 HFE/JAK2, 1 JAK2/TFR2, 2 with TFR2/EGLN1, 1 VHL/HFE, 1 TFR2/HFE) and 3 mutated genes in 5 patients (1 EGLN1/EPO-R/HFE, 1 VHL/HFE/EGLN1, 1 EPAS1/EPO-R/HFE, 1 EPAS1/HFE/EGLN1 and HFE/TFR2/JAK2). All the mutations found were germline. Interestingly, 21 out of the 27 (78%) patients carrying HFE mutation displayed 2 or more mutations. Summary/Conclusion: The use of NGS panels in various clinical conditions has frequently demonstrated that multiple mutations coexist in various patients and that the monogenic diseases are quite rare. This study is the first at our best knowledge that gives evidence of more than one mutated gene in erythrocytotic patients, and this is the results of the use of an appropriate NGS panel. The data here reported suggest that we can confirm that HFE mutations are common in IE patients, in some cases associated with other mutations, but the present data ask some questions: HFE mutations alone can induce erythrocytosis? or other genetic imbalances are needed? The presence of multiple mutations could lead to a greater severity of the disease? A significant number of IE patients displayed TFR2 mutations, giving more relevance to the hypothesis of the iron metabolism implication in IE genesis. Finally, the presence of 11 patients carrying germlines JAK2 mutations is surprising, and we suppose it will be necessary to strictly watch these patients in the suspicion of a future appearance of a polycythemia vera. The present study demonstrates the need to extend the biomolecular knowledge in patients with idiopathic erythrocytosis.