Erythrocytosis is a disease with an increased number of erythrocytes. Primary erythrocytosis is caused by defect within the bone marrow, while secondary by defect outside the bone marrow. Familial erythrocytosis is a disorder with genetic sequence variations in genes (EPOR, EGLN1, EPAS1, VHL, EPO, HBB, HBA1, HBA2 in BPGM) involved in oxygen sensing pathways or oxygen transport. HBA genes encode for the hemoglobin (Hb) alpha chains, and sequence variants in these genes can cause high-affinity Hb forms. The oxygen bound to these variants is not successfully released into the tissue, causing hypoxia of the tissue and increased erythrocyte production. Using databases, we have obtained all known sequence variants causing (Hb) with high affinity to oxygen associated with familial erythrocytosis type 7 (ECYT7). We developed a protocol for identification of sequence variants in the HBA genes using polymerase chain reaction (PCR) and Sanger sequencing. We analyzed two patients with suspected familial erythrocytosis, differentiated between both paralogs but found no sequence variants associated with ECYT7. We established the protocol for sequencing the HBA1 and HBA2 genes in patients with suspected familial erythrocytosis.
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