[Erythrocytosis after hematopoietic stem cell transplantation: report of 3 cases and literature review].

This is a report of three cases of three male patients. One of the patients had myelodysplastic syndrome, and two had aplastic anemia; their ages were 28, 32, and 21 years old, respectively. Two patients underwent sibling allogeneic hematopoietic stem cell transplantation, and one underwent haploidentical hematopoietic stem cell transplantation. All the patients showed elevated hemoglobin and hematocrit at 6, 16, and 9 months after transplantation, with normal white blood cells and platelets and no splenomegaly. All causes of secondary polycythemia were ruled out. Bone marrow morphology showed no erythroid hyperplasia. The PCR result for BCR-ABL (P210, P230, P190, and variants) was negative, and there were no mutations at the amino acid site 617 of JAK2, exon 12 of JAK2, exon 9 of CALR, and amino acid site 515 of MPL. All three patients had hypertension. One patient was treated with amlodipine, and the other two patients were treated with angiotensin receptor blockers. The durations of erythrocytosis for these three patients were 6 years and 3 months, 4 years and 7 months, and 5 years and 3 months, respectively through December 2022. There was no tendency for spontaneous remission. Erythrocytosis after hematopoietic stem cell transplantation is a rare complication. Previous reports in the literature suggest that the mechanism of post-transplant erythrocytosis in recipients of allogeneic hematopoietic stem cell transplantation may be different from that of recipients of other transplants.