A candidate transacting modulator of fetal hemoglobin gene expression in the Arab-Indian haplotype of sickle cell anemia.

Fetal hemoglobin (HbF) levels are higher in the Arab-Indian (AI) ß-globin gene haplotype of sickle cell anemia compared with African-origin haplotypes. To study genetic elements that effect HbF expression in the AI haplotype we completed whole genome sequencing in 14 Saudi AI haplotype sickle hemoglobin homozygotes-seven selected for low HbF (8.2% ± 1.3%) and seven selected for high HbF (23.5% ± 2.6%). An intronic single nucleotide polymorphism (SNP) in ANTXR1, an anthrax toxin receptor (chromosome 2p13), was associated with HbF. These results were replicated in two independent Saudi AI haplotype cohorts of 120 and 139 patients, but not in 76 Saudi Benin haplotype, 894 African origin haplotype and 44 AI haplotype patients of Indian origin, suggesting that this association is effective only in the Saudi AI haplotype background. ANTXR1 variants explained 10% of the HbF variability compared with 8% for BCL11A. These two genes had independent, additive effects on HbF and together explained about 15% of HbF variability in Saudi AI sickle cell anemia patients. ANTXR1 was expressed at mRNA and protein levels in erythroid progenitors derived from induced pluripotent stem cells (iPSCs) and CD34+ cells. As CD34+ cells matured and their HbF decreased ANTXR1 expression increased; as iPSCs differentiated and their HbF increased, ANTXR1 expression decreased. Along with elements in cis to the HbF genes, ANTXR1 contributes to the variation in HbF in Saudi AI haplotype sickle cell anemia and is the first gene in trans to HBB that is associated with HbF only in carriers of the Saudi AI haplotype. Am. J. Hematol. 91:1118-1122, 2016. © 2016 Wiley Periodicals, Inc.

BCL11A enhancer haplotypes and fetal hemoglobin in sickle cell anemia.

BACKGROUND: Fetal hemoglobin (HbF) levels in sickle cell anemia patients vary. We genotyped polymorphisms in the erythroid-specific enhancer of BCL11A to see if they might account for the very high HbF associated with the Arab-Indian (AI) haplotype and Benin haplotype of sickle cell anemia. METHODS AND RESULTS: Six BCL112A enhancer SNPs and their haplotypes were studied in Saudi Arabs from the Eastern Province and Indian patients with AI haplotype (HbF ~20%), African Americans (HbF ~7%), and Saudi Arabs from the Southwestern Province (HbF ~12%). Four SNPs (rs1427407, rs6706648, rs6738440, and rs7606173) and their haplotypes were consistently associated with HbF levels. The distributions of haplotypes differ in the 3 cohorts but not their genetic effects: the haplotype TCAG was associated with the lowest HbF level and the haplotype GTAC was associated with the highest HbF level and differences in HbF levels between carriers of these haplotypes in all cohorts were approximately 6%. CONCLUSIONS: Common HbF BCL11A enhancer haplotypes in patients with African origin and AI sickle cell anemia have similar effects on HbF but they do not explain their differences in HbF.

Splenic complications of the sickling syndromes and the role of splenectomy.

PURPOSE: To analyze the authors' experience with splenectomy for sickling disorders and evaluate the indications, complications, and outcome. PATIENTS AND METHODS: Over a period of 10 years (1987-1997), 113 patients with sickling disorders (100 with sickle cell disease and 13 with sickle-beta-thalassemia) had splenectomy at the authors' hospital as part of their management. The indications for splenectomy were hypersplenism (26 patients), major splenic sequestration crisis (MSSC) (23 patients), minor recurrent splenic sequestration crisis (MRSSC) (50 patients), splenic abscess (12 patients), and massive splenic infarction (2 patients). RESULTS: Splenectomy in patients with sickle cell disease (SCD) and sickle-beta-thalassemia (S-beta-Thal) was beneficial in reducing their transfusion requirements and its attendant risks, eliminating the discomfort from mechanical pressure of the enlarged spleen, and avoiding the risks of acute splenic sequestration crisis. It also was curative for patients with splenic abscess and massive splenic infarction. Twenty-four patients with SCD (24%) had splenectomy and cholecystectomy caused by concomitant gallstones. There was no mortality, and the postoperative morbidity was 7%. CONCLUSIONS: With careful perioperative management, splenectomy is both safe and beneficial in a select group of patients with SCD and S-beta-Thal.

Splenectomy for hematological diseases: The Qatif Central Hospital experience.

BACKGROUND: In the Eastern Province of Saudi Arabia, an area known for various hemoglobinopathies, splenectomy is performed rather frequently. This study is an analysis of our experience with splenectomy performed for various hematological disorders between 1988 and 1997, outlining the indications, complications and outcome. PATIENTS AND METHODS: This is a retrospective analysis of all patients who had splenectomy at our hospital during this period. One hundred and forty-three patients were treated for various hematological disorders at our hospital. These disorders included sickle cell disease (SCD) (100 patients), sickle ss-thalassemia (S-ss-thal) (13 patients), ss-thalassemia major (15 patients), Hb H disease (3 patients), idiopathic thrombocytopenic purpura (ITP) (5 patients), Gaucherâs disease (2 patients), hereditary spherocytosis (1 patient), autoimmune hemolytic anemia (1 patient), thalassemia intermediate (2 patients) and chronic myeloid leukemia (1 patient). RESULTS: The indications for splenectomy in those with SCD and S-ss-thal were: hypersplenism (26 patients), major splenic sequestration crisis (23 patients), minor recurrent splenic sequestration crisis (50 patients), splenic abscess (12 patients), and massive splenic infarction (2 patients). Splenectomy in these patients was beneficial in reducing their transfusion requirements and its attendant risks, eliminating the discomfort from mechanical pressure of the enlarged spleen, avoiding the risks of acute splenic sequestration crisis, and managing splenic abscess. For those with thalassemia, total splenectomy was beneficial in reducing their transfusion requirements, while partial splenectomy was beneficial only as a temporary measure, as regrowth of splenic remnant in these patients subsequently led to increase in their transfusion requirements. Those with ITP, hereditary spherocytosis, and autoimmune hemolytic anemia showed excellent response following splenectomy. There was no mortality, and the postoperative morbidity was 5.6%. CONCLUSION: With careful perioperative management, splenectomy is both safe and beneficial in a selected group of patients with hematological diseases.