Significance of genetic modifiers of hemoglobinopathies leading towards precision medicine.

Hemoglobinopathies though a monogenic disorder, show phenotypic variability. Hence, understanding the genetics underlying the heritable sub-phenotypes of hemoglobinopathies, specific to each population, would be prognostically useful and could inform personalized therapeutics. This study aimed to evaluate the role of genetic modifiers leading to higher HbF production with cumulative impact of the modifiers on disease severity. 200 patients (100 ß-thalassemia homozygotes, 100 Sickle Cell Anemia), and 50 healthy controls were recruited. Primary screening followed with molecular analysis for confirming the ß-hemoglobinopathy was performed. Co-existing α-thalassemia and the polymorphisms located in 3 genetic loci linked to HbF regulation were screened. The most remarkable result was the association of SNPs with clinically relevant phenotypic groups. The γ-globin gene promoter polymorphisms [- 158 C → T, + 25 G → A],BCL11A rs1427407 G → T, - 3 bp HBS1L-MYB rs66650371 and rs9399137 T → C polymorphisms were correlated with higher HbF, in group that has lower disease severity score (P < 0.00001), milder clinical presentation, and a significant delay in the age of the first transfusion. Our study emphasizes the complex genetic interactions underlying the disease phenotype that may be a prognostic marker for predicting the clinical severity and assist in disease management.

The Changing Trends in Prenatal Diagnosis of Hemoglobinopathies in India: The Quest of a Single Center to Reduce the Burden of Disease over Three Decades.

The ß-thalassemias and sickle cell disorders pose a considerable health burden in India. Of the more than 10,000 annual births of children with a severe hemoglobinopathy, only around 10.0% are managed optimally. Thus, genetic counseling and prenatal diagnosis (PND) is a valid option for a large and diverse country. Our center was one of the first to initiate PND and we present our experience over 30 years to evaluate the impact of awareness in changing the trends of PND of hemoglobinopathies. Both second and first-trimester diagnoses were undertaken by fetoscopy/cordocentesis and globin biosynthesis/high-performance liquid chromatography (HPLC) analysis of fetal blood and chorionic villus sampling (CVS) and DNA analysis. Over 30 years, 3478 couples (first trimester: 2475; second trimester: 1003) from all over India were offered PND. The number of couples coming in the first trimester increased significantly over each decade and couples coming prospectively increased from 2.5 to 18.4%. A cost-effective stepwise approach was used for molecular analysis. Eight hundred and one fetuses (23.0%) were affected and all except three couples opted for termination of these pregnancies. Genetic counseling and PND is the only way to reduce the burden of disease. With awareness, there was a shift from second trimester to first trimester PND over each decade, with an increasing number of couples coming during the first pregnancy. There are only 15 to 20 centers in India offering PND. We have compared our study with other reports on PND from different regions in India.

Genotypic-phenotypic heterogeneity of 뫧-thalassemia and hereditary persistence of fetal hemoglobin (HPFH) in India.

Large deletions in the ß-globin gene cluster lead to increased HbF levels by delaying the γ- to ß-globin switch process. However, these deletions when inherited as a homozygous condition or when co-inherited with ß-thalassemia result in variable clinical phenotypes. Individuals or families with a clinically presenting child, where the parents had HbF levels ≥ 10%, were further screened for the presence of large ß-globin cluster deletions. Six deletions in the ß-globin gene cluster were screened by GAP-PCR, and the uncharacterized deletions were further analyzed by gene dosage or by multiplex ligation-dependent probe amplification (MLPA). Among 192 individuals suspected for the inheritance of large deletions, 138 were heterozygous for large deletions, 45 were compound heterozygous of a large ß-globin cluster deletion and ß-thalassemia, and 9 were found to be homozygous for deletions. Among the heterozygotes, the Asian Indian inversion-deletion was found to be the most common deletion (39.9%), followed by the HPFH-3 deletion (30.0%). Other deletions 49.3 kb, δß-thalassemia (21.2%), and 32.6 kb deletion (4.4%) were also found to be prevalent in our population. Patients compound heterozygous or homozygous for HPFH-3 and 32.6 kb deletions showed a milder clinical presentation, as compared with the patients compound heterozygous or homozygous for the Asian Indian inversion-deletion and 49.3 kb δß-thalassemia. This comprehensive study highlights the mutation spectrum of large ß-globin cluster deletions and the clinical heterogeneity in the patients homozygous or compound heterozygous with ß-thalassemia, thus asserting the need for molecular characterization of these deletions.

Prevalence of globin gene modifiers encountered in fetuses during antenatal diagnosis of hemoglobinopathies.

INTRODUCTION: The hemoglobinopathies are the commonest group of single gene disorders in the Indian subcontinent. Although genetic modifiers are known to have a remarkable effect on phenotypic expression, the effects of the possible co-inheritance of different modifiers are not taken into account during prenatal diagnosis. The present study was undertaken to look for the frequency of globin gene modifiers like the types of ß-globin gene mutations, α thalassemia, α gene triplication, and the Xmn1 polymorphism in fetuses during antenatal diagnosis of hemoglobinopathies. MATERIALS AND METHODS: A total of 580 fetuses with different diagnoses were screened for the presence of genetic modifiers. RESULTS: Twenty-two different ß-globin gene mutations were identified of which 3.5% were milder mutations. Among the affected fetuses, 29.6% of the ß-thalassemia major and 52.9% of the sickle cell anemia (SCA) fetuses had one genetic modifier while 3.7% of the ß-thalassemia major and 41.1% of the SCA fetuses had co-inherited two modifiers. α-gene triplication was detected in 16 (3.5%) ß-thalassemia/sickle cell heterozygous and normal fetuses of which 5 babies (2 ß-thalassemia heterozygous and 3 normal) could be followed up. Of the 2 ß-thalassemia heterozygous babies, one had a severe clinical presentation. CONCLUSION: Many fetuses had one or two gene modifiers. However, the impact of these on ameliorating the severity of the disease could not be evaluated as all the fetuses with ß thalassemia major or sickle cell disease were terminated. Parents having heterozygous fetuses with α gene triplication should be followed up periodically after birth for better management of these babies.

The phenotypic and molecular diversity of hemoglobinopathies in India: A review of 15 years at a referral center.

INTRODUCTION: The hemoglobinopathies pose a significant health burden in India. Apart from the ß thalassemias and sickle cell disorders, α thalassemias and structural hemoglobin variants are also common. Here we have reviewed the phenotypic and molecular diversity of hemoglobinopathies encountered at a referral center in western India over a period of 15 years. MATERIALS AND METHODS: Screening for hemoglobinopathies was done using HPLC and cellulose acetate electrophoresis. Molecular characterization was done using Covalent Reverse Dot Blot Hybridization (CRDB), Amplification Refractory Mutation System (ARMS), GAP PCR and direct DNA sequencing. RESULTS: The study includes 31 075 individuals who were referred for diagnosis of hemoglobinopathies and prenatal diagnosis. Of these 14 423 individuals showed various hemoglobin abnormalities. Beta genotyping in 5615 individuals showed the presence of 49 ß thalassemia mutations. 143 ß thalassemia heterozygotes had normal or borderline HbA2 levels. We identified three δ gene mutations (HbA2 Pellendri, HbA2 St.George, HbA2 Saurashtra) in ß thalassemia heterozygotes leading to normal HbA2 levels. The commonest defects among the raised Hb F determinants were Gγ(Αγδß)0 Indian inversion and the HPFH-3 Indian deletion. A total of 312 individuals showed the presence of α thalassemia, of which 12.0% had a single α gene deletion (-α/αα). HbH disease was identified in 29 cases with 10 different genotypes. Alpha globin gene triplication was seen in 2.1% of ß thalassemia heterozygotes with a thalassemia intermedia phenotype. Seven unusual α chain variants and eight uncommon ß chain variants were identified. CONCLUSION: The repertoire of molecular defects seen in the different globin genes will be valuable for management and control of these disorders both in India as well as in other countries where there is a huge influx of migrant populations from India.

Prenatal Diagnosis of HbE-ß-Thalassemia: Experience of a Center in Western India.

The clinical presentation of HbE-ß-thalassemia is extremely variable, however, many cases are severe and transfusion dependent. We offered prenatal diagnosis to 108 couples, 20 of whom came prospectively. CVS was done in 93 cases (9.5-13 weeks of gestation) while amniocentesis/cordocentesis was done for 15 cases in the second trimester. Diagnosis was done by reverse dot blot hybridization, ARMS, DNA sequencing and in a few cases by HPLC analysis of fetal blood. The genetic combinations in the couples at-risk were the following: HbE trait/ß-thal trait-95, HbE-thal/HbE trait-5, HbE homozygous/ß-thal trait-3, HbE-thal/ß-thal trait-3, HbE Lepore/ß-thal trait-1, HbE trait/HbDPunjab trait-1. IVS1-5(G>C) was the commonest ß-thalassemia mutation followed by codon15(G>A), codon30(G>C), codons41/42(-CTTT), the 619 bp deletion and codon8/9(+G) in the ß-thalassemic parent. However, several rare mutations seen in India like -90(C>T), -88(C>T),codon15(-T), IVS1-129(A>C), IVS1-130(G>C), IVSII-1(G>A), IVSII-837(C>T) and IVSII 848(C>A) were also encountered. Twenty-one fetuses were affected (HbE-ß-thal-20, ß-thal major-1) and all the couples opted for termination of the pregnancies. Couples with affected children wish to undergo prenatal testing for HbE-ß-thal in subsequent pregnancies. More regional centers are needed for these services, particularly in West Bengal and the North-East where HbE is very common.

Rare ß- and δ-Globin Gene Mutations in the Pathare Prabhus: Original Inhabitants of Mumbai, India.

Genetic structure of the Indian population is influenced by waves of several immigrants from West Eurasia. Therefore, genetic information of various ethnic groups is valuable to understand their origins, the pattern of migration as well as the genetic relationship between them. No genetic data is available on Pathare Prabhu, which is a small indigenous Hindu community from Mumbai, Maharashtra State, India. The aim of this study was to screen the Pathare Prabhus for hemoglobinopathies, which is a major public health problem in India. Two hundred and fifty-seven unrelated Pathare Prabhus subjects were screened for various hemoglobinopathies. Complete blood counts (CBC) were done on an automated hematology counter. High performance liquid chromatography (HPLC) was used to identify ß-thalassemia (ß-thal) carriers. Molecular characterization of the ß gene defects was done by reverse dot-blot hybridization, amplification refractory mutation system (ARMS) and DNA sequencing. Deletional α-thalassemia (α-thal) was detected by multiplex polymerase chain reaction (PCR). Hb A2-Saurashtra (HBD: c.301C>T) was identified by DNA sequencing; its modeling was also done. The prevalence of ß-thal was 3.89%, while deletional α-thal was 5.4%. The initiation codon (ATG>ACG) (HBB: c.2T>C) was seen in eight individuals (80.0%), Hb D-Punjab (HBB: c.364G>C) and Hb A2-Saurashtra, was found in two and one individual, respectively. A community-specific ß-thal mutation was found in Pathare Prabhus in significant proportions. This information is useful in developing an algorithm for a prenatal diagnosis (PND) program.

Hb E-ß-Thalassemia in Five Indian States.

Hb E [ß26(B8)Glu→Lys; HBB: c.79G > A]-ß-thalassemia (ß-thal) has an extremely variable clinical presentation. We report the clinical features of these patients from five Indian states together with their hematological and molecular characteristics. Seventy-eight Hb E-ß-thal patients from different regions [West Bengal (30), Maharashtra (21), Uttar Pradesh (13), Bihar (11), Orissa (3)] were clinically evaluated along with hematological profiles and molecular characteristics (ß-thal mutations, XmnI polymorphisms, α genotypes). Twenty-nine of the 78 patients had a mild clinical presentation (clinical score 2.2 ± 1.1), while 15 had moderate severity (clinical score 6.1 ± 1.2) with occasional transfusion needs, and 34 patients were severely affected (clinical score 8.2 ± 0.5) requiring regular blood transfusions. The age at clinical presentation in the severely affected patients was lower (6 months-10 years) as compared to those with milder symptoms (2 years-34 years). Thirty-four patients showed splenomegaly (spleen ≥3 cm below the costal margin) and five patients were splenectomized. The severe ß+ IVS1-5 (G > C) (HBB: c.92 + 5G > C) was the most common ß-thal mutation, while seven other mutations were also seen. The XmnI [+/+] and [-/-] polymorphisms were seen in 24.1 and 10.3% of mildly affected patients and 14.7 and 17.6% of severely affected patients respectively. A single α gene deletion (-α3.7/αα) was found in 20.7% of mildly affected and 5.9% of severely affected patients, respectively. No specific differences in the clinical, hematological or molecular characteristics were observed in the Hb E-ß-thal patients from various geographic regions or different ethnic groups.

Five Rare ß Globin Chain Hemoglobin Variants in India.

Thalassemias as well as structural hemoglobin (Hb) variants are common monogenic inherited disorders of Hb in India. In this paper we describe 5 rare ß-chain Hb variants identified in the Indian population on the basis of high performance liquid chromatography (HPLC). Of these 3 were identified during antenatal screening of ß-thalassemia while the other 2 cases were referred to us for a diagnostic work up. These 5 Hb variants were Hb British Columbia (ß CD 101 GAG â†’ AAG), Hb Saint Louis (ß CD28 CTG â†’ CAG), Hb G Coushatta (ß CD 22 GAA â†’ GCA), Hb Pyrgos (ß CD 83 GGC â†’ GAC) and Hb Agenogi (ß CD 90 GAG â†’ AAG). Hb Saint Louis and Hb G Coushatta eluted in the HbA2 window, Hb British Columbia and Hb Agenogi eluted in the Hb C window while Hb Pyrgos eluted in an unknown window on HPLC. They were all identified by DNA sequencing. The child having Hb St. Louis had hepatosplenomegaly and anemia while the individuals with the other 4 variants were asymptomatic. Rare Hb variants are diagnostic curiosities that may be encountered by laboratories. Correct identification requires the application of more than one technique to avoid misdiagnosing them as more common variants (e.g. St. Louis and G Coushatta as E or D Iran on HPLC. Some, like G Coushatta may interfere with HPLC-based HbA1c estimation).

Challenges in prenatal diagnosis of beta thalassaemia: couples with normal HbA2 in one partner.

OBJECTIVES: To undertake ß-genotyping in couples having normal/borderline HbA2 levels in one partner to offer the possibility of prenatal diagnosis of thalassaemia. METHODS: A total of 967 couples were screened for ß-thalassaemia. Haematological analysis was carried out on a Sysmex K-1000 analyser. The HbA2 and HbF levels were measured by High Performance Liquid Chromatography-Variant II analyser (Bio-Rad, USA). ß-globin gene analysis was done by reverse dot blot hybridization, amplification refractory mutation system or DNA sequencing. Alpha globin gene triplication was determined by Multiplex PCR. RESULTS: In 33 of 967 couples, one partner had a normal/borderline HbA2 level (1-3.5%); however a ß-thalassaemia mutation could be identified in 24 of these individuals. Molecular analysis of the ß-globin gene revealed the presence of the capsite +1 (A → C) [HBB: c.-50 A → C] mutation in 15 cases (60%), Poly A(T → C) [HBB: c.*110 T → C] mutation in two cases (8%), IVS 1-5 (G → C) [HBB: c. 92 + 5 (G → C)] mutation in four cases (17%) and the CD 15 (G → A) [HBB: c. 47 G → A] mutation, CD 16 (-C) [HBB: c. 51 del C] mutation and CD 30 (G → C) [HBB: c. 93 G → C] mutation in one case each (4%). Alpha gene triplication was found in five cases, while four cases remained uncharacterized. CONCLUSIONS: ß-genotyping should always be done in a couple if one partner is a ß-thalassaemia carrier irrespective of the RBC indices and HbA2 levels of the other partner.

Diverse phenotypes and transfusion requirements due to interaction of ß-thalassemias with triplicated α-globin genes.

Co-inheritance of triplicated α-genes can alter the clinical and hematological phenotypes of ß-thalassemias. We evaluated the phenotypic diversity and transfusion requirements in ß-thalassemia heterozygotes, homozygotes, and normal individuals with associated α-gene triplication. Clinical and hematological evaluation was done and the ß-thalassemia mutations characterized by a covalent reverse dot blot hybridization/amplification refractory mutation system. Alpha-globin gene triplication was assessed by multiplex PCR. During the last 2.5 years, 181 ß-thalassemia patients and ß-thalassemia carriers with an unusual clinical presentation were referred to us for screening for the presence of associated α-globin gene triplication. Twenty-nine of them had associated α-gene triplication (3 ß-thalassemia homozygotes or compound heterozygotes and 26 ß-thalassemia heterozygotes). One ß-thalassemia compound heterozygote [IVS 1-5 (G → C) + CD 41/42 (-CTTT)] was anemic at birth and required blood transfusions unusually early by 6 weeks of age. The second patient (4.5 years) was also clinically severe and became transfusion dependent in spite of having one mild ß-thalassemia mutation [Capsite +1 (A → C)]. The third case (3.5 years) who was homozygous for a mild ß-gene mutation [-88 (C → T)] with α gene triplication was untransfused. The 26 ß-thalassemia heterozygotes with associated triplicated α-genes presented variably, with a ß-thalassemia intermedia-like presentation. While screening the family members of all these cases, we found another 10 ß-thalassemia heterozygotes and 9 normal individuals with α-globin gene triplication; however, all of them were asymptomatic. Beta-thalassemia carriers, homozygotes, and compound heterozygotes with an unusual presentation should be screened for the possible presence of associated α-globin gene triplication which could influence the clinical and hematological presentation.

HbD Punjab/HbQ India Compound Heterozygosity: An Unusual Association.

BACKGROUND: Haemoglobinopathies are the commonest hereditary disorders in India and pose a major health problem. Both beta thalassaemia and structural haemoglobin variants are relatively common in northwestern India. Here we report a 29-year-old Sindhi female who was referred to us for a haemoglobinopathy work up and genetic counseling since her spouse was a classical beta thalassaemia carrier. METHOD: A complete blood count was done on an automated cell counter. Haemoglobin analysis was carried out using HPLC Variant Haemoglobin Testing System. The cellulose acetate electrophoresis was carried out [pH 8.9]. Confirmation of mutations was done by automated DNA sequencing. RESULTS: HPLC analysis showed four major peaks, HbA0, a peak in the HbD window, an unknown peak [retention time 4.74 minutes] and a peak in the HbC window. The HbA2 level was 2.2%, and the HbF level was 0.7%. Cellulose acetate electrophoresis at alkaline pH, a slow moving band was seen at the HbS/D position along with a prominent band at the HbA2 position. DNA sequencing of the ß and α genes showed presence of the two hemoglobin variants: Hb D [ß 121GAA → CAA] and Hb Q [α 64 AAG → GAG]. The δ globin gene was normal. The additional peak in the HbC window was due to the formation of a heterodimer hybrid. CONCLUSION: Both HbD Punjab and HbQ India are relatively common in India, but their co-inheritance has not been described in the country. This case is the third report of compound heterozygosity for HbQ India/HbD Punjab haemoglobinopathy globally and the second one from India.

Clinical and hematological presentation among Indian patients with common hemoglobin variants.

BACKGROUND: Co-inheritance of structural hemoglobin variants like HbS, HbD(Punjab) and HbE can lead to a variable clinical presentation and only few cases have been described so far in the Indian population. METHODS: We present the varied clinical and hematological presentation of 22 cases (HbSD(Punjab) disease-15, HbSE disease-4, HbD(Punjab)E disease-3) referred to us for diagnosis. RESULTS: Two of the 15 HbSD(Punjab) disease patients had moderate crisis, one presented with mild hemolytic anemia; however, the other 12 patients had a severe clinical presentation with frequent blood transfusion requirements, vaso occlusive crisis, avascular necrosis of the femur and febrile illness. The 4 HbSE disease patients had a mild to moderate presentation. Two of the 3 HbD(Punjab)E patients were asymptomatic with one patient's sibling having a mild presentation. The hemoglobin levels of the HbSD(Punjab) disease patients ranged from 2.3 to 8.5 g/dl and MCV from 76.3 to 111.6 fl. The hemoglobin levels of the HbD(Punjab)E and HbSE patients ranged from 10.8 to 11.9 and 9.8 to 10.0 g/dl whereas MCV ranged from 67.1 to 78.2 and 74.5 to 76.0 fl respectively. CONCLUSIONS: HbSD(Punjab) disease patients should be identified during newborn screening programmes and managed in a way similar to sickle cell disease. Couple at risk of having HbSD(Punjab) disease children may be given the option of prenatal diagnosis in subsequent pregnancies.

Hemoglobin Fontainebleau [a21(B2)Ala>Pro]: The second report from India.

Structural hemoglobin (Hb) variants are mainly due to point mutations in the globin genes resulting in single amino acid substitutions. Until date, about 200 alpha chain variants have been identified and they are usually detected during the hemoglobinopathy screening programs. Under a community control program for hemoglobinopathies, which involved screening of antenatal cases followed by prenatal diagnosis if indicated. Here, we report a rare alpha globin gene variant Hb Fontainebleau [a21(B2)Ala>Pro] detected in the heterozygous condition in a 35-year-old pregnant lady screened during this program. This is the second report of this alpha globin variant from India. Unlike the earlier case from India where Hb Fontainebleau was reported in a neonate who was also a carrier of Hb Sickle and had no clinical problems, this case presented with a bad obstetric history associated with the secondary infertility. However, the presence of the variant and the obstetric complications may be unrelated.

Molecular characterization of ß-thalassemia in four communities in South Gujarat--codon 30 (G → A) a predominant mutation in the Kachhiya Patel community.

Different thalassemia mutations have been reported in various ethnic groups and geographical regions in India. In this study, we have investigated Kachhiya Patel, Dhodia Patel, Modh Bania, and Muslim communities of Surat, Gujarat to identify molecular defects causing ß-thalassemia in them. Covalent reverse dot blot hybridization technique was used to detect six common Indian ß-thalassemia mutations while the seventh mutation (619-bp deletion) was identified by PCR. The less common mutations were detected by amplification refractory mutation and the uncharacterized samples were directly sequenced. Characterization of ß-thalassemia mutations was carried out in a total of 175 unrelated ß-thalassemia trait cases. We identified IVS 1 nt 5 (G → C) in 31 out of 65 Muslims, codon (Cd) 41/42 (-CTTT) in 14 out of 16 in Modh Banias, Cd 15 (G → A) in 19 out of 24 Dhodia Patels. The most significant observation was an uncommon mutation; Cd 30 (G → A) detected in 61 out of 70 Kachhiya Patels. The 619-bp deletion was detected in 6 out of 10 Muslim-Memons. Many other rare mutations like Cd 15 (-T), Cd 8 (-AA), -88 (C → A), Capsite +1 (A → C), Cd 16(-C), and Cd 5 (-CT) were detected. To our knowledge, our study is the first to characterize ß-thalassemia mutations in the Kachhiya Patel community. This study will facilitate molecular analysis and prenatal diagnosis in these four communities.

Antenatal screening for identification of couples for prenatal diagnosis of severe hemoglobinopathies in surat, South gujarat.

PURPOSE: Our aim was to identify couples at risk of having a homozygous or compound heterozygous child with a severe hemoglobinopathy by antenatal screening and prenatal diagnosis in Surat, South Gujarat. METHOD: Pregnant women were screened for hemoglobinopathies by means of red cell indices, the solubility test, cellulose acetate electrophoresis tests, and confirmation by HPLC. Husbands of the pregnant women having hemoglobinopathies were counseled and screened for hemoglobinopathies. The couples at risk were again counseled and referred to the National Institute of Immunohematology, where mutations in parents and fetuses were identified by molecular analysis. After prenatal diagnosis, the continuing pregnancies were followed up and infants were tested at birth. RESULTS: Out of 3,009 women, 37.04, 52.6, and 10.3 % were in the first, second, and third trimester of pregnancy, respectively. Among those having hemoglobinopathies, 102 (3.38 %) had the ß-thalassemia trait, 46 (1.5 %) the Sickle cell trait, and 26 (0.86) had hemoglobin variants like Hb DPunjab, Hb E, Hb DIran, Hb QIndia, Hb JParis-I, and Hb OIndonesia. Out of the 14 couples at risk of having an affected child, 11 (78.5 %) couples opted for prenatal diagnosis. Three fetuses had homozygous ß-thalassemia and hence the pregnancies were terminated. Follow up of normal or heterozygous fetuses confirmed the diagnosis. CONCLUSION: During antenatal screening, we found many Hb variants of ß and α globin chains. Late antenatal registration, non-cooperation of the husband for investigation, and refusal for prenatal diagnosis are the main hurdles in the hemoglobinopathy prevention program and awareness is necessary.

Variable haematological and clinical presentation of ß-thalassaemia carriers and homozygotes with the Poly A (T→C) mutation in the Indian population.

OBJECTIVES: To study the varied clinical and haematological profile of ß-thalassaemia homozygotes, compound heterozygotes and heterozygotes with the Poly A (T→C) mutation and its implication in prenatal diagnosis. MATERIALS AND METHODS: Forty individuals were included in the study. Peripheral smear examination, complete blood count and haemoglobin analysis were carried out. ß-thalassaemia mutation analysis was carried out by reverse-dot-blot hybridization, amplification refractory mutation system and DNA sequencing of the ß-globin gene. RESULTS: Five of the six ß-thalassaemia homozygotes with the Poly A (T→C) mutation and five individuals who were compound heterozygous for the Poly A (T→C) mutation along with another common Indian ß-thalassaemia mutation showed a severe ß-thalassaemia major phenotype, while one individual presented as a thalassaemia intermedia. Majority of the 28 heterozygous individuals with this mutation showed borderline HbA2 (mean HbA2 = 3.7 ± 0.4%) levels as compared to individuals with common ß-thalassaemia mutations (mean HbA2 = 5.2 ± 1.4%). The Mean Corpuscular Volume (MCV) levels in individuals heterozygous for the Poly A (T→C) mutation (mean MCV 70.0 ± 5.2 fl) were significantly higher than in individuals with other common ß-thalassaemia mutations (mean MCV 60.7 ± 7.7 fl) (P < 0.001). CONCLUSION: It is important to identify these often silent carriers of ß-thalassaemia for prenatal diagnosis as homozygotes have a severe disease.