Iron overload in Chinese patients with hemoglobin H disease

Αlpha-thalassemia: A practical overview

α-Thalassemia is an inherited blood disorder characterized by decreased synthesis of α-globin chains that results in an imbalance of α and β globin and thus varying degrees of ineffective erythropoiesis, decreased red blood cell (RBC) survival, chronic hemolytic anemia, and subsequent comorbidities. Clinical presentation varies depending on the genotype, ranging from a silent or mild carrier state to severe, transfusion-dependent or lethal disease. Management of patients with α-thalassemia is primarily supportive, addressing either symptoms (eg, RBC transfusions for anemia), complications of the disease, or its transfusion-dependence (eg, chelation therapy for iron overload). Several novel therapies are also in development, including curative gene manipulation techniques and disease modifying agents that target ineffective erythropoiesis and chronic hemolytic anemia. This review of α-thalassemia and its various manifestations provides practical information for clinicians who practice beyond those regions where it is found with high frequency.

Clinical and genetic characteristics of hemoglobin H disease in Iran

Hemoglobin H (Hb H) disease is a subtype of α-thalassemia caused by deletional and/or non-deletional mutations in three alpha-globin genes in which the various genotypes determine the disease severity. This study was aimed to investigate the frequency of alpha gene mutations and genotypes and their correlation with hematological and clinical characteristics in Iran. Among 202 patients diagnosed with Hb H disease through a national study in Iran according to standard methods, we had access to the hematologic and clinical findings and genetic data of 101 patients in whom genetic study was performed. Genomic DNA from peripheral blood was extracted and analyzed for identification of α-globin gene mutations using Multiplex Gap Polymerase Chain Reaction, Reverse Hybridization Assay, and finally Direct DNA Sequencing method. Twenty-one different mutations and thirty genotypes were detected in 101 patients with Hb H disease. In total, 39 patients (38.6%) were deletional and 62 patients (61.4%) were non-deletional type of the disease. The _--^MED mutation was highly prevalent in almost half of the patients (56.4%). Among various genotypes, -^MED/-a^3.7 (29.7%) and -α^20.5/-α^5NT (6.9%) were the most prevalent genotypes found in the studied group. Patients with non-deletional type presented with more severe hematological and clinical findings. Hb H percentage and serum ferritin levels were significantly higher in non-deletional patients in comparison to the deletional group (p < 0.05). 12 (11.9%) and 40 (39.6%) out of 101 patients were on regular and occasional transfusions, respectively. 83% of those with regular transfusion belonged to the non-deletional group. Among transfusion-dependent patients, -^MED/α^CSα and α^20.5/-α^5NT were the most common genotypes. In this study, two patients with -α^20.5/α^CSα and -^MED/α^-5NT genotypes experienced thrombotic events. This study indicated that although non-deletional genotypes of Hb H disease were responsible for more clinical severity of the disease, due to the presence of severe phenotypes even in deletional types, no definite correlation was found between genotype and phenotype.

Increasing prevalence of thalassemia in America: Implications for primary care

Thalassemia, once a rarity in the United States, is increasingly encountered in clinical practice due to shifts in immigration. Early carrier screening in at-risk populations can help clinicians implement genetic counseling and prevent new cases. Chronic transfusions are the mainstay of therapy for patients with severe thalassemia (beta thalassemia major), and are used intermittently in individuals with milder forms of thalassemia (Hb H/H Constant Spring disease and beta thalassemia intermedia). Iron overload is a major source of morbidity and mortality in individuals with transfusion and non-transfusion-dependent thalassemia, necessitating iron chelation therapy. Iron overload contributes to increased risk of cirrhosis, heart failure, and endocrinopathies, while ineffective erythropoiesis and hemolysis contribute to multiple complications, including splenomegaly, extramedullary hematopoiesis, pulmonary hypertension, and thrombosis. An understanding of the importance of carrier screening, complications, monitoring, and management strategies, coupled with collaboration with a hematologist with thalassemia expertise, is essential to reduce the morbidity and mortality in patients with thalassemia.

Splenectomy improves anaemia but does not reduce iron burden in patients with haemoglobin H Constant Spring disease

BACKGROUND

Splenectomy is reported to increase the haemoglobin level in patients with haemoglobin H Constant Spring (HbH CS) disease; however, its impact on iron burden and the underlying mechanism remains unclear.

MATERIALS AND METHODS

From March through to May 2013, a total of 50 adults with HbH CS disease (25 cases splenectomised and 25 cases non-splenectomised) were enrolled. The patients' general conditions, history of blood transfusion and iron chelator treatment were investigated. Levels of haemoglobin, nucleated red blood cell counts, and serum ferritin were measured. The percentage of apoptotic erythroid precursor cells in bone marrow, an index representing ineffective erythropoiesis, was determined in some cases.

RESULTS

There were no significant differences in age, blood transfusion volume, and use of iron chelator drugs between the splenectomised group and the non-splenectomised group. Significantly higher haemoglobin levels, serum ferritin levels and nucleated red blood cell counts as well as a higher percentage of apoptotic erythroid progenitor cells were detected in the splenectomised group. Regression analysis revealed that age and nucleated red blood cell counts were independent risk factors affecting the serum ferritin level.

DISCUSSION

Despite improving the haemoglobin level, splenectomy is associated with greater iron burden in HbH CS disease. A high nucleated red blood cell count is predictive of the risk of severe iron overload.

Hyperferritinemia and hyperuricemia may be associated with liver function abnormality in obese adolescents

BACKGROUND

The iron status in human body and its association with liver function in adolescents was rarely studied. The objective was to investigate the association among the levels of serum ferritin, uric acid and alanine aminotransferase (ALT) in adolescents.

METHODS AND RESULTS

A total of 2090 adolescents negative for hepatitis B surface antigen from one junior high school (786, 12-13 years), three senior high schools (973, 15-16 years) and one college (331, 18-19 years) participated in this survey. Anthropometric and biochemical measurements, including complete blood count, ALT, serum ferritin and uric acid were performed. An ALT>42 U/L was defined as elevated, a ferritin level >200 µg/L was defined as hyperferritinemia. A uric acid level >460 µmol/L in males and >340 µmol/L in females was defined as hyperuricemia. The chi-squared test, linear regression and multivariate logistic regression were used for the data analysis. Elevated ALT levels were detected in 76 (3.6%) students and were more prevalent in males than females (6.4% vs. 2.0%, p<0.001). The univariate analysis found gender, age group, body mass index, ferritin level, uric acid level and white blood cell count all to be significantly associated with elevated ALT. Linear regression showed a positive correlation among log(ferritin), uric acid level and ALT level. Elevated ALT occurred more frequently at ferritin level >100 µg/L. The logistic regression analysis found that body mass index, hyperferritinemia and hyperuricemia were significant factors associated with the ALT elevation, but gender, age, and white blood cell count were not.

CONCLUSIONS

Hyperferritinemia and hyperuricemia are two independently significant factors associated with ALT elevation among obese adolescents. More studies are needed to corroborate any hypothesis related to these phenomena.

Ineffective erythropoiesis and thalassemias

PURPOSE OF REVIEW

In thalassemia, ineffective erythropoiesis is characterized by apoptosis of the maturing nucleated erythroid cells. New studies also suggest that limited erythroid cell differentiation plays a role in the development of ineffective erythropoiesis. This would further exacerbate anemia and increase iron absorption.

RECENT FINDINGS

During erythroid differentiation and maturation, it is critical that the components of hemoglobin are made in stoichiometric amounts. It is, therefore, conceivable that factors that modify this process intrinsically or extrinsically will also affect erythropoiesis. Several proteins have the potential to alter erythroid replication and differentiation in conditions of ineffective erythropoiesis. Elevated erythropoietin levels increase the number of erythroid precursors bearing a phosphorylated form of Jak2. This, in a pathological condition, may contribute to limited erythroid differentiation. Unbalanced synthesis of globins and heme modifies the activity of the heme-regulated inhibitor kinase, affecting proliferation and differentiation of the erythroid precursors. In addition, inefficient elimination of reactive oxygen species, which are increased under conditions of iron overload, may also hamper erythropoiesis.

SUMMARY

Use of Jak2 inhibitors may limit the overproduction of immature erythroid cells in thalassemia, with the potential of reversing extramedullary hematopoiesis and preventing splenectomy. In addition, preventing iron overload and formation of reactive oxygen species may also be beneficial in limiting tissue damage and ineffective erythropoiesis.

Iron overload in the Asian community

Hereditary hemochromatosis is an iron overload disorder that can lead to the impairment of multiple organs and is caused by mutations in one or more different genes. Type 1 hemochromatosis is the most common form of the disease and results from mutations in the HFE gene. Juvenile hemochromatosis (JH) is the most severe form, usually caused by mutations in hemojuvelin (HJV) or hepcidin (HAMP). The autosomal dominant form of the disease, type 4, is due to mutations in the SLC40A1 gene, which encodes for ferroportin (FPN). Hereditary hemochromatosis is commonly found in populations of European origin. By contrast, hemochromatosis in Asia is rare and less well understood and can be masked by the presence of iron deficiency and secondary iron overload from thalassemia. Here, we provide a comprehensive report of hemochromatosis in a group of patients of Asian origin. We have identified novel mutations in HJV, HAMP, and SLC40A1 in countries not normally associated with hereditary hemochromatosis (Pakistan, Bangladesh, Sri Lanka, and Thailand). Our family studies show a high degree of consanguinity, highlighting the increased risk of iron overload in many countries of the developing world and in countries in which there are large immigrant populations from these regions.

Clinical and molecular analysis of haemoglobin H disease in Sardinia: haematological, obstetric and cardiac aspects in patients with different genotypes

In this study, 251 Sardinian patients (187 adults and 64 children) with haemoglobin (Hb) H disease were evaluated. Two-hundred and sixteen patients (86%) had the deletional type (- -/-alpha) and 36 (14%) patients had the non-deletional type (- -/alpha(ND)alpha). A clear genotype-phenotype correlation was found, with the non-deletional type more severe than the deletional type. Diagnosis of Hb H disease was incidental in about 60% of cases. Aplastic crises due to B19 parvovirus infection were found in five patients (2.1%), while 23 patients (9.6%) experienced one or more haemolytic crises. Nineteen patients with Hb H received sporadic red blood cell transfusions and three patients were repeatedly transfused. Forty-seven of 61 married women (77%) had 82 pregnancies. In children, mean serum ferritin was 87 +/-92 mug/l and in adults, was 192 +/- 180 mug/l in females and 363 +/- 303 mug/l in males. For the 98 male patients, a significant correlation was found between ferritin values and age (r2 = 0.33, P < 0.0001). In the Sardinian population, Hb H disease needs regular monitoring for early detection and treatment of possible complications, such as worsening of anaemia that may require red cell transfusion, cholelithiasis and iron overload.

Hemoglobinopathies in pregnancy

Hemoglobinopathies represent a unique set of genetic disorders. Formerly, many affected individuals did not survive to childbearing age. Affected women now commonly reach childbearing age and desire pregnancy. Successful pregnancy is possible in many cases with carefully coordinated obstetric and medical management. Genetic screening and prenatal diagnosis is an important aspect of prenatal care in these disorders. DNA mutation analysis offers rapid and accurate fetal diagnosis. Pregnancy also offers a unique situation in that cord blood has become a valuable source of stem cells for transplant. This allows the potential role of the unaffected fetus as a donor for affected siblings. In addition, it was proposed that the fetus may be able to act as a donor of stem cells for an affected mother. Despite current screening recommendations,many couples are not aware that they are carriers; it is common for a child to be born with an unexpected, serious hemoglobinopathies. For this reason, newborn screening programs have been introduced in most high-risk areas. Early diagnosis can facilitate implementation of proper preventive health measures, education of the parents regarding their carrier status, and provide the child with ongoing comprehensive care.

Genetic and clinical features of hemoglobin H disease in Chinese patients

BACKGROUND

Normally, one pair of each of the two alpha-globin genes, alpha1 and alpha2, resides on each copy of chromosome 16. In hemoglobin H disease, three of these four alpha-globin genes are affected by a deletion, a mutation, or both. We studied the alpha1-globin gene abnormalities and the clinical and hematologic features of Chinese patients with hemoglobin H disease in Hong Kong.

METHODS

We assessed the clinical features, hematologic values, serum ferritin levels, and liver function of 114 patients with hemoglobin H disease. We also performed echocardiography and magnetic resonance imaging of the liver and examined the two pairs of alpha-globin genes.

RESULTS

Hemoglobin H disease in 87 of the 114 patients (76 percent) was due to the deletion of three of the four alpha-globin genes (--/-alpha), a combination termed the deletional type of hemoglobin H. The remaining 27 patients (24 percent) had the nondeletional type of hemoglobin H disease, in which two alpha-globin genes are deleted and a third is mutated (--/alphaalphaT). All 87 patients with the deletional type of hemoglobin H were double heterozygotes in whom there was a deletion of both alpha-globin genes from one chromosome, plus a deletion of the alpha1 or alpha2 gene from the other chromosome (--/alpha- or --/-alpha). A variety of mutated alpha-globin genes was found in the patients with nondeletional type of hemoglobin H disease. Patients with the nondeletional type of the H disease had more symptoms at a younger age, more severe hemolytic anemia, and larger spleens and were more likely to require transfusions than patients with deletional hemoglobin H disease. The severity of iron overload was not related to the genotype.

CONCLUSIONS

Chinese patients in Hong Kong with the nondeletional type of hemoglobin H disease have more severe disease than those with the deletional type of the disease. Iron overload is a major cause of disability in both forms of the disease.

Hemosiderosis with diabetes mellitus in untransfused Hemoglobin H disease

A 37-year-old untransfused, non-drinking man with Hemoglobin H-CS disease presented with insulin-dependent diabetes mellitus, markedly elevated serum ferritin level, and marked iron deposition in hepatocytes. He did not carry either of the two common mutations of the HLA-H gene for hereditary hemochromatosis, namely, Cys282Tyr and His68Asp, nor did he have the associated HLA marker (HLA-A3, B7 nor B-14) for the disease. Patient with HbH disease should be monitored for iron overload.

Non-HLA-linked hemochromatosis in a Chinese woman

A 55 year-old Chinese woman is described with severe iron overload similar in degree and distribution to that seen in hereditary hemochromatosis in the Caucasian population. Autopsy findings confirmed severe iron overload in the liver, pancreas, skin, heart, and endocrine organs. Hepatic iron concentration was 482 mumol/g with a hepatic iron index of 8.8. There was no history of thalassemia, transfusions, or alcohol abuse. Pedigree analysis revealed two HLA identical brothers that had no clinical or biochemical evidence of iron overload. This case is an unusual example of severe iron overload in a non-Caucasian kindred and may represent a non-HLA-linked form of iron overload.