Genotypic-phenotypic heterogeneity of δβ-thalassemia and hereditary persistence of fetal hemoglobin (HPFH) in India.
印度 δ β-地中海贫血的基因型-表型异质性和胎儿血红蛋白 (HPFH) 的遗传性持续性。
- 作者列表："Hariharan P","Kishnani P","Sawant P","Gorivale M","Mehta P","Kargutkar N","Colah R","Nadkarni A
:Large deletions in the β-globin gene cluster lead to increased HbF levels by delaying the γ- to β-globin switch process. However, these deletions when inherited as a homozygous condition or when co-inherited with β-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 β-globin cluster deletions. Six deletions in the β-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 β-globin cluster deletion and β-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, δβ-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 δβ-thalassemia. This comprehensive study highlights the mutation spectrum of large β-globin cluster deletions and the clinical heterogeneity in the patients homozygous or compound heterozygous with β-thalassemia, thus asserting the need for molecular characterization of these deletions.
: β-珠蛋白基因簇中的大量缺失通过延迟 γ-至 β-珠蛋白转换过程导致HbF水平增加。然而，当作为纯合状态遗传或当与 β-地中海贫血共同遗传时，这些缺失导致可变的临床表型。有临床表现的儿童的个体或家庭，其父母的HbF水平 ≥ 10%，进一步筛查是否存在大的 β-珠蛋白簇缺失。通过GAP-PCR筛选 β-珠蛋白基因簇中的6个缺失，并通过基因剂量或多重连接依赖性探针扩增 (MLPA) 进一步分析未表征的缺失。在192例疑似遗传大缺失的个体中，138例为杂合大缺失，45例为复合杂合大 β-珠蛋白簇缺失和 β-地中海贫血，9例为纯合缺失。在杂合子中，发现亚洲印第安倒位缺失是最常见的缺失 (39.9%)，其次是HPFH-3缺失 (30.0%)。其他缺失49.3 kb，δ β-地中海贫血 (21.2%) 和32.6 kb缺失 (4.4%) 也在我们的人群中普遍存在。与亚洲印第安人倒位缺失和32.6 kb δ β-地中海贫血的患者相比，HPFH-3和49.3 kb缺失的复合杂合子或纯合子患者的临床表现较轻.这项全面的研究突出了大 β-珠蛋白簇缺失的突变谱和 β-地中海贫血纯合或复合杂合患者的临床异质性，从而表明需要对这些缺失进行分子鉴定。
METHODS:BACKGROUND:Thalassemia is one of the most common monogenetic diseases in the south of China and Southeast Asia. Hemoglobin Bart's hydrops fetalis syndrome was caused by a homozygous Southeast Asian deletion (-/-) in the HBA gene. Few studies have proved the potential of screen for Bart's hydrops fetalis using fetal cell-free DNA. However, the number of cases is still relatively small. Clinical trials of large samples would be needed. OBJECTIVE:In this study, we aimed to develop a noninvasive method of target-captured sequencing and genotyping by the Bayesian method using cell-free fetal DNA to identify the fetal genotype in pregnant women who are at risk of having hemoglobin Bart hydrops fetalis in a large-scale study. STUDY DESIGN:In total, 192,173 couples from 30 hospitals were enrolled in our study and 878 couples were recruited, among whom both the pregnant women and their husbands were detected to be carriers of Southeast Asian type (-/αα) of α-thalassemia. Prenatal diagnosis was performed by chorionic villus sampling, amniocentesis, or cordocentesis using gap-polymerase chain reaction considered as the golden standard. RESULTS:As a result, we found that the sensitivity and specificity of our noninvasive method were 98.81% and 94.72%, respectively, in the training set as well as 100% and 99.31%, respectively, in the testing set. Moreover, our method could identify all of 885 maternal samples with the Southeast Asian carrier and 36 trisomy samples with 100% of sensitivity in T13, T18, and T21 and 99.89% (1 of 917) and 99.88% (1 of 888) of specificity in T18 and T21, respectively. CONCLUSION:Our method opens the possibility of early screening for maternal genotyping of α-thalassemia, fetal aneuploidies in chromosomes 13/18/21, and hemoglobin Bart hydrops fetalis detection in 1 tube of maternal plasma.
METHODS:OBJECTIVES:Sickle cell disease (SCD) is a serious illness with disabling acute and chronic pain that needs better therapies, but insufficient patient participation in research is a major impediment to advancing SCD pain management. The purpose of this article is to discuss the challenges of conducting an SCD study and approaches to successfully overcoming those challenges. DESIGN:In a repeated-measures, longitudinal study designed to characterize SCD pain phenotypes, we recruited 311 adults of African ancestry. Adults with SCD completed 4 study visits 6 months apart, and age- and gender-matched healthy controls completed 1 visit. RESULTS:We recruited and completed measures on 186 patients with SCD and 125 healthy controls. We retained 151 patients with SCD with data at 4 time points over 18 months and 125 healthy controls (1 time point) but encountered many challenges in recruitment and study visit completion. Enrollment delays often arose from patients' difficulty in taking time from their complicated lives and frequent pain episodes. Once scheduled, participants with SCD cancelled 49% of visits often because of pain; controls canceled 30% of their scheduled visits. To facilitate recruitment and retention, we implemented a number of strategies that were invaluable in our success. CONCLUSION:Patients' struggles with illness, chronic pain, and their life situations resulted in many challenges to recruitment and completion of study visits. Important to overcoming challenges was gaining the trust of patients with SCD and a participant-centered approach. Early identification of potential problems allowed strategies to be instituted proactively, leading to success.
METHODS:OBJECTIVES:Sickle cell anemia is the commonest genetic disorder in India, and the frequency of the sickle cell gene is very high in the remote tribal areas where facilities are generally limited. Therefore, a rapid and affordable point-of-care test for sickle cell disease is needed. METHODS:The diagnostic accuracy of HemoTypeSC was evaluated against automated high-performance liquid chromatography (HPLC) as the gold standard for its efficacy in a newborn screening program. RESULTS:A total of 1,559 individuals (980 newborns and 579 adults) from four participating centers were analyzed by both methods. HemoTypeSC correctly identified 209 of 211 total hemoglobin (Hb) SS cases, for a 99.1%/99.9% total HbSS sensitivity/specificity. Overall, HemoTypeSC exhibited sensitivity and specificity of 98.1% and 99.1% for all possible phenotypes (HbAA, HbAS, and HbSS) detected. HPLC is relatively expensive and not available in most laboratories in remote tribal areas. CONCLUSIONS:We conclude that the rapid, point-of-care testing device HemoTypeSC test is suitable for population and newborn screening for the HbS phenotype.