Outcomes of pregnancies complicated by haemoglobin H-constant spring and deletional haemoglobin H disease: A retrospective cohort study

Disease burden, management strategies, and unmet needs in α-thalassemia due to hemoglobin H disease

Alpha-thalassemia is an inherited blood disorder caused by impaired α-globin chain production, leading to anemia and other complications. Hemoglobin H (HbH) disease is caused by a combination of mutations generally affecting the expression of three of four α-globin alleles; disease severity is highly heterogeneous, largely driven by genotype. Notably, non-deletional mutations cause a greater degree of ineffective erythropoiesis and hemolysis, higher transfusion burden, and increased complication risks versus deletional mutations. There are limited treatment options for HbH disease, and effective therapies are needed. This review discusses the pathophysiology of HbH disease, current management strategies, unmet needs, and emerging treatment options.

Regulation of N6-methyladenosine modification in erythropoiesis and thalassemia

In eukaryotic RNA, N6-methyladenosine (m6A) is a prevalent form of methylation modification. The m6A modification process is reversible and dynamic, written by m6A methyltransferase complex, erased by m6A demethylase, and recognized by m6A binding proteins. Through mediating RNA stability, decay, alternative splicing, and translation processes, m6A modification regulates gene expression at the post-transcriptional level. Erythropoiesis is the process of hematopoietic stem cells undergoing proliferation, a series of differentiation and maturation to form red blood cells (RBCs). Thalassemia is a common monogenic disease characterized by excessive production of ineffective RBCs in the peripheral circulation, resulting in hemolytic anemia. Increasing evidence suggests that m6A modification plays a crucial role in erythropoiesis. In this review, we comprehensively summarize the function of m6A modification in erythropoiesis and further generalize the mechanism of m6A modification regulating ineffective erythropoiesis and fetal hemoglobin expression. The purpose is to improve the understanding of the pathogenesis of erythroid dysplasia and offer new perspectives for the diagnosis and treatment of thalassemia.

Fertility and Pregnancy in Women with Transfusion-Dependent Thalassemia

Because women with transfusion-dependent thalassemia are seeking pregnancy, ensuring the best outcomes for both mother and baby require concerted and collaborative efforts between the hematologist, obstetrician, cardiologist, hepatologist, and genetic counselor among others. Proactive counseling, early fertility evaluation, optimal management of iron overload and organ function, and application of advances in reproductive technology and prenatal screening are important in ensuring a healthy outcome. Many unanswered questions remain requiring further study, including fertility preservation, non-invasive prenatal diagnosis, chelation therapy during pregnancy, and indications and duration of anticoagulation.

The Clinical Phenotypes of Alpha Thalassemia

Clinical manifestations of α-thalassemia range from no symptoms to severe transfusion-dependent anemia. Alpha thalassemia trait is deletion of 1 to 2 α-globin genes, whereas α-thalassemia major (ATM; Barts hydrops fetalis) is the deletion all 4 α genes. All other genotypes of intermediate severity are categorized as HbH disease, a vastly heterogenous group. Clinical spectrum is classified as mild, moderate, and severe by symptoms and need for intervention. Anemia in prenatal period may be fatal without intrauterine transfusions. New therapies to modify HbH disease or provide cure for ATM are under development.

Life beyond alpha-thalassaemia: We are moving forward

In the not so distant past, pregnancy in thalassaemia patients was considered a very high risk and often not recommended. The results regarding alpha-thalassaemia and in particular haemoglobin H disease by Srimeuniwai and colleagues are very encouraging. Nowadays thalassaemic women not only become pregnant, but maternal outcome is not decreased compared to controls. Commentary on: Ake-sittipaisarn, et al. Outcomes of pregnancies complicated by haemoglobin H-Constant Spring and deletional haemoglobin H disease: A retrospective cohort study. Br J Haematol 2022 (Online ahead of print). doi:10.1111/bjh.18338.