Roshan Colah

Effect of α-thalassemia on sickle-cell anemia linked to the Arab-Indian haplotype in India

Two population groups from Western India with a high prevalence of the βs gene, one tribal (Valsad) and the other nontribal (Nagpur), were studied. The βs gene frequency in both populations was similar (0.22 vs. 0.23), but not the clinical expression of sickle‐cell anemia (SS): the sickle homozygotes in the tribal group appeared to have a mild clinical course, whereas the majority in the nontribal group exhibited a more severe clinical phenotype. Both tribal and nontribal SS patients had a similarly high mean hemoglobin (Hb)F expression (18.5% vs. 15.5%) and a high number of F cells (72.3% vs. 66.6%). DNA analysis of the β‐globin gene cluster region revealed that in these two populations, this portion of DNA was identical with and corresponded to the typical Arab‐Indian haplotype. Nevertheless, in heterozygotes, the mean βs expression was lower (27.9%) in the tribal as compared to the nontribal group (35.5%). The major epistatic factor distinguishing the milder presentation in tribals vs. a more severe manifestation in nontribals was the very high frequency (0.97) of the α‐thalassemia gene in the former as compared to the latter (0.24). We conclude that the phenotypic expression of sickle‐cell anemia, linked to the Arab‐India haplotype and expressing similar levels of HbF and F cells, is not uniformly mild in India and that α‐thalassemia is a powerful and additional epistatic factor in the Indian subcontinent. Am. J. Hematol. 55:104‐109, 1997.

Global burden, distribution and prevention of β-thalassemias and hemoglobin E disorders

The β-thalassemias, including the hemoglobin E disorders, are not only common in the Mediterranean region, South-East Asia, the Indian subcontinent and the Middle East but have now become a global problem, spreading to much of Europe, the Americas and Australia owing to migration of people from these regions. Approximately 1.5% of the global population are heterozygotes or carriers of the β-thalassemias. While the overall frequencies of carriers of these disorders are known in most countries, there have been few attempts at micromapping and wherever this has been done, significant variations are seen even within small geographic regions. Thus, the figures for the estimated numbers of births each year of homozygous β-thalassemia and the severe compound states involving other hemoglobin disorders may be an underestimate. Screening strategies have varied from premarital to antenatal in different countries depending on socio–cultural and religious customs in different populations. Prenatal diagnosis programs are ongoing in many countries and the knowledge of the distribution of mutations has facilitated the establishment of successful control programs. Many of these were through North–South partnerships and networking. Yet, there are many countries in Asia where they are lacking, and South–South partnerships are now being developed in South-East Asia and the Indian subcontinent to link centers with expertise to centers where expertise needs to be developed. Although the carrier frequencies will remain unaltered, this will eventually help to bring down the burden of the birth of affected children with β-thalassemias and hemoglobin E disorders in Asia.

Frequency of β-thalassemia trait and other hemoglobinopathies in northern and western India

INTRODUCTION: India is an ethnically diverse country with an approximate population of 1.2 billion. The frequency of beta-thalassemia trait (βTT) has variously been reported from <1% to 17% and an average of 3.3%. Most of these studies have been carried out on small population groups and some have been based on hospital-based patients. There is also a variation in the prevalence of hemoglobinopathies in different regions and population groups in the country. A high frequency of Hb D has been reported from the North in the Punjabi population, Hb E in the eastern region of India and Hb S is mainly reported from populations of tribal origin from different parts of the country. OBJECTIVES: To study the gene frequency of βTT and other hemoglobinopathies in three regions East (Kolkata), West (Mumbai) and North (Delhi) in larghe population group (schoolchildren) for a more accurate assessment of gene frequency for planning of control programmes for haemoglobinopathies. MATERIALS AND METHODS: This study included 5408 children from 11 schools in Delhi, 5682 from 75 schools in Mumbai and 957 schoolchildren from Kolkata who were screened for βTT and haemoglobinopathies. These included 5684 children from 75 schools in Mumbai and 5408 children from 11 schools in Delhi. Children were 11-18 years of age of both sexes. The final report is, however, only on 11090 schoolchildren from Mumbai and Delhi as data from Kolkata was restricted both in numbers and objectives and could not be included for comparison. RESULTS: The overall gene frequency of βTT in Mumbai and Delhi was 4.05% being 2.68% and 5.47% in children of the two cities respectively. In Mumbai, the gene frequency was evenly distributed. Majority of the children with βTT from Mumbai were from Marathi (38.9%) and Gujarati (25%) speaking groups. Gene frequency was >5% in Bhatias, Khatris, Lohanas and Schedule Castes. In Delhi, a higher incidence was observed in schoolchildren of North and West Delhi (5.8-9.2%). The schoolchildren of North and West Delhi comprised predominantly of Punjabi origin compared to children in the South of the city (2.2%, 2.3%). When analyzed state-wise, the highest incidence was observed in children of Punjabi origin (7.6%) and was >4% from several other states. Majority of the traits from Mumbai were anemic (95.1% male and 85.6% in female). The prevalence of anemia was lower (62.7% male and 58.4% female) children with βTT from Delhi. This was a reflection of the higher prevalence of anemia in children without hemoglobinopathy in Mumbai than in Delhi. Nutritional deficiency was probably more severe and rampant in children Mumbai. Gene frequency of Hb D was greater in schoolchildren from Delhi (1.1%) than in Mumbai (0.7%). Hb S trait (0.2%) was observed exclusively in children from Mumbai. A low incidence of Hb E trait (0.04%) was seen in children in Mumbai. A higher incidence is reported from the East. The number of cases studied from the eastern region was small as the data from the East (Kolkata) could not be included in the analysis. CONCLUSION: This study comprises a larger number of children studied for the gene frequency of βTT and other hemoglobinopathies from India. Population groups with higher gene frequencies require screening programmes and facilities for antenatal diagnosis as well as increased awareness and educational programmes to control the birth of thalassemic homozygotes. The overall carrier frequency of βTT was 4.05% and reinforces the differential frequency of β-thalassemia trait in schoolchildren from Delhi and Mumbai and the higher incidence of hemoglobin D in Punjabis as reported previously. The birth incidence calculated thereof for homozygous thalassemics would be 11,316 per year which are added each year to the existing load of homozygous thalassemics. This is much higher than the previously reported number of births annually. Hence suitable control measures need to be undertaken urgently in India.

Response to hydroxyurea in β thalassemia major and intermedia: Experience in western India

BACKGROUND The clinical and hematological response to hydroxyurea was evaluated in beta thalassemia patients in western India with variable clinical severity and correlated with genetic factors. MATERIALS AND METHODS Seventy-nine patients-[38-beta thalassemia intermedia-(group I), 41-beta thalassemia major-(group II)] on hydroxyurea therapy were followed-up for 20-24months. RESULTS Among the frequently transfused patients in group I, 58% became transfusion independent and 16% showed a 50% reduction in transfusions after therapy which correlated with a higher mean fold increase in HbF and gamma mRNA expression levels. Forty-one percent of patients in group I had associated alpha-thalassemia and 72.7% were XmnI (+/+). beta thalassemia chromosomes among the responders of group I (41%) were linked to haplotype (- + + - + + - - +) as against haplotype (+ - - - - - - - +) being more common among the non-responders. Response was not linked to the beta thalassemia mutations. Thirty-two percent of group II patients showed a 50% reduction in their transfusion requirements after therapy which also correlated with a higher mean fold increase in HbF and gamma mRNA expression levels. A significant decrease in serum ferritin was seen in both groups. 19% of patients could not tolerate the drug. CONCLUSIONS In group I, clinical response to hydroxyurea was better in patients with alpha-thalassemia, XmnI (+/+) and a higher mean fold increase in gamma mRNA expression. In group II, only one-third of patients showed a partial response.

Hydroxyurea in sickle cell disease--a study of clinico-pharmacological efficacy in the Indian haplotype.

There is clinical variability in the presentation of sickle cell disease among Indians. Vaso-occlusive crisis is common among non-tribal patients. Hydroxyurea, induces fetal hemoglobin (HbF) synthesis and reduces the clinical severity of sickle cell disease but individual patients have a variable response. This study was undertaken to investigate the efficacy and safety of hydroxyurea in Indians with severe manifestations where the beta(s) gene is linked to the Arab-Indian haplotype and is associated with higher HbF levels. Seventy-seven patients (29 adult sickle homozygous, 25 pediatric sickle homozygous, 23 adult sickle beta-thalassemia) selected for hydroxyurea therapy were evaluated for clinical, hematological, biochemical and genetic parameters and were followed for 24 months. Ninety-eight point seven percent of the sickle chromosomes were linked to the Arab-Indian haplotype, 27% of patients had associated alpha thalassemia and 65% were Xmn I +/+. Seventy-eight percent of the patients had no further crises after starting hydroxyurea. This effect was accompanied by a significant increase in HbF (p<0.001), but this increase was variable in individual cases. There was also an increase in gamma gene mRNA expression in the few cases so studied. Hemoglobin levels increased significantly (p<0.001) resulting in the cessation of blood transfusions. Leucopoenia was observed in one patient. Hydroxyurea was effective in reducing the clinical severity in Indian patients who initially had higher HbF levels and the presence of ameliorating factors, such as alpha-thalassemia and the Xmn I polymorphism. Hydroxyurea therapy with careful monitoring can thus change the quality of life of Indians with sickle cell disease.

Regional heterogeneity of β-thalassemia mutations in the multi ethnic Indian population

To determine the frequencies of beta-thalassemia mutations in different states of India and to compare this with the available data in Asian Indians for a comprehensive catalogue of molecular defects in the Indian population. beta-thalassemia mutations were characterized in 2456 heterozygotes using reverse dot blot hybridization, ARMS and DNA sequencing. 36 beta-thalassemia mutations were characterized from 18 different states in India. Seven mutations were common, accounting for 95.8% of mutated alleles. Marked regional diversity was seen in different parts of the country. Among the tribal populations, only 2 mutations (IVS I-5 (G-->C) and CD15 (G-->A) accounted for over 90% of mutant alleles. A compilation of all the studies in Asian Indians reported so far showed the presence of 63 mutations in the Indian population. This large study adds to the existing data to give a detailed account of the molecular basis of beta-thalassemia in India. This information is important for establishing prenatal diagnosis programmes in different states in India as well as other countries in which there is a major influx of Indian immigrants.

Factor VIII and IX gene polymorphisms and carrier analysis in Indian population

The efficacy of the three common intra‐ and extragenic polymorphic sites of the factor VIII and IX genes has been examined in the Indian population, with an aim to develop a strategy that would be accurate and informative, yet economical. The approach for hemophilia A carrier detection includes tests for Bcll, Xbal, and Taql polymorphic sites for introns 18 and 22 and the extragenic locus St 14, respectively, whereas for hemophilia B, tests include detection of Taql, Ddel, and Hhal polymorphic sites for introns 4 and 1, and the 3′ flanking region of the factor IX gene, respectively. In hemophilia A, the cumulative efficiency of these three polymorphisms has been found to be 100%, since all 37 tested families were informative for at least one of these three polymorphisms. It is of interest to note that a case of recombination between St 14 and the factor VIII gene was also observed. Of the 47 unrelated X chromosomes examined (normal = 10, factor VIII:C deficiency = 37), heterozygosity for Bcll, Xbal, and St 14 was found to be 47%, 36%, and 86%, respectively, in the factor VIII gene. However, when 37 unrelated X chromosomes (normal = 10, factor IX:C = 27) were analyzed for polymorphism with Taql, Ddel, and Hhal, it was found that the polymorphism detection rate was only 18% for the Taql site but 45% each for the Ddel and Hhal sites, in the factor IX gene. This indicates a low effectiveness of the Taql restriction site in carrier analysis of hemophilia B families in our population. Am. J. Hematol. 54:271–275, 1997

Epidemiology of β‐thalassaemia in Western India: mapping the frequencies and mutations in sub‐regions of Maharashtra and Gujarat

Although the average frequency of β‐thalassaemia carriers in India is 3–4% and the prevalent mutations have been studied, no micromapping has been done. This is the first attempt to provide an accurate estimate of the frequencies of β‐thalassaemia and the expected annual births of homozygous children in different districts of Maharashtra and Gujarat in Western India as well as to determine the molecular heterogeneity in different sub‐regions in these states. A total of 18 651 individuals were screened for haemo‐globinopathies and mutations were characterized in 1334 β‐thalassaemia heterozygotes. There was an uneven distribution of the frequencies of β‐thalassaemia, varying from 1·0% to 6·0% and 0% to 9·5% in different districts of Maharasthra and Gujarat. The rate of homozygosity per 1000 births annually was 0·28 in Maharashtra and 0·39 in Gujarat. The three most prevalent β‐thalassaemia mutations in Maharashtra were IVS 1‐5(G→C), Codon 15(G→A) and Codon 30(G→C) (87·9%) while in Gujarat they were IVS 1‐5(G→C), 619 bp deletion and Codon 5(‐CT) (68·5%). These data will help to develop adequate programmes for control and care where they are most needed. They also emphasize the importance of subgroup micromapping for determining the health burden of a common genetic disease.

Glucose–6–phosphate dehydrogenase deficiency in India

Glucose–6–phosphate dehydrogenase (G6PD) deficiency is the commonest red cell enzymopathy in humans and has an X-linked inheritance. It has been reported from India more than 30 years ago and the prevalence varies from 0–27% in different caste, ethnic and linguistic groups. The major clinical manifestations are drug induced hemolytic anemia, neonatal jaundice and chronic non–spherocytic hemolytic anemia. Individuals with G6PD deficiency have a selective advantage against falciparum malaria. Thirteen biochemically characterized variants have been reported from India. At the molecular level, G6PD Mediterranean is the most common deficient variant in the caste groups whereas, G6PD Orissa is more prevalent among the tribal of India. The third common variant seen in India is G6PD Kerala–Kalyan

Flow cytometric osmotic fragility—An effective screening approach for red cell membranopathies

Among the red cell membrane disorders, hereditary spherocytosis (HS) is one of the most common causes of inherited hemolytic anemia. The aim of this study was to compare the flow‐cytometric approach for screening of red cell membrane disorders based on osmotic fragility with the eosin‐5‐maleimide (E5′M) dye test. A group of β‐thalassemia heterozygotes were also studied.