Ivy Ng

International reproducibility of single breathhold T2* MR for cardiac and liver iron assessment among five thalassemia centers.

To examine the reproducibility of the single breathhold T2* technique from different scanners, after installation of standard methodology in five international centers.

Multi-center transferability of a breath-hold T2 technique for myocardial iron assessment

BackgroundCardiac iron overload is the leading cause of death in thalassemia major and is usually assessed using myocardial T2* measurements. Recently a cardiovascular magnetic resonance (CMR) breath-hold T2 sequence has been developed as a possible alternative. This cardiac T2 technique has good interstudy reproducibility, but its transferability to different centres has not yet been investigated.Methods and ResultsThe breath-hold black blood spin echo T2 sequence was installed and validated on 1.5T Siemens MR scanners at 4 different centres across the world. Using this sequence, 5–10 thalassemia patients from each centre were scanned twice locally within a week for local interstudy reproducibility (n = 34) and all were rescanned within one month at the standardization centre in London (intersite reproducibility). The local interstudy reproducibility (coefficient of variance) and mean difference were 4.4% and -0.06 ms. The intersite reproducibility and mean difference between scanners were 5.2% and -0.07 ms.ConclusionThe breath-hold myocardial T2 technique is transferable between Siemens scanners with good intersite and local interstudy reproducibility. This technique may have value in the diagnosis and management of patients with iron overload conditions such as thalassemia.

Amelioration of oxidative stress in red blood cells from patients with β-thalassemia major and intermedia and E-β-thalassemia following administration of a fermented papaya preparation.

In β‐hemoglobinopathies, such as β‐thalassemia (thal) and sickle cell anemia, the primary defects are mutations in the β‐globin gene. However, many aspects of the pathophysiology are mediated by oxidative stress. Fermented papaya preparation (FPP), a natural health food product obtained by biofermentation of carica papaya, has been shown to limit oxidative stress both in vitro and in vivo. We studied the effect of FPP on two groups of β‐thal patients: β‐thal, major and intermedia, (in Israel) and E‐β‐thal (in Singapore). The results indicated that in both groups FPP treatment increased the content of reduced glutathione (GSH) in red blood cells (RBC), and decreased their reactive oxygen species (ROS) generation, membrane lipid peroxidation, and externalization of phosphatidylserine (PS), indicating amelioration of their oxidative status, without a significant change in the hematological parameters. Since the turnover of the erythron is relatively slow, it is possible that longer duration of treatment, probably with the addition of an iron chelator, is required in order to achieve the latter goals. Copyright

FMR1 CGG repeat patterns and flanking haplotypes in three Asian populations and their relationship with repeat instability.

Hyper‐expansion of a CGG repeat in the 5′ untranslated region of the FMR1 gene followed by methylation and silencing is the predominant cause of Fragile X syndrome, the most common inherited mental retardation disorder. Most detailed studies of the FMR1 gene have focused on Caucasian populations and patients. We performed a detailed haplotype and linkage disequilibrium analysis of the FMR1 gene in a total of 454 unselected normal X chromosomes from three Asian populations, Chinese, Malay and Indian. Compared to Caucasians and African Americans, the diversity of normal FMR1 CGG repeat lengths, patterns and flanking haplotypes were lower in Asians. Strong linkage disequilibrium was observed between the CGG repeat and flanking FMR1 markers in all three Asian populations, with strong association between specific CGG repeat alleles and flanking marker alleles observed only in the Chinese and Malays. A test for randomness of distribution between FRAXA CGG repeat patterns and flanking FMR1 marker haplotypes also revealed a highly significant non‐random distribution between CGG repeat patterns and flanking haplotypes in all three ethnic groups (P < 0.001). Extending previous findings in Caucasians and African Americans we present a novel statistical approach, using data from unselected population samples alone, to show an association between absence of at least one AGG interruption in any position (5′, 3′, or middle) and increased CGG repeat instability.

Massively Parallel Sequencing of Patients with Intellectual Disability, Congenital Anomalies and/or Autism Spectrum Disorders with a Targeted Gene Panel

Developmental delay and/or intellectual disability (DD/ID) affects 1–3% of all children. At least half of these are thought to have a genetic etiology. Recent studies have shown that massively parallel sequencing (MPS) using a targeted gene panel is particularly suited for diagnostic testing for genetically heterogeneous conditions. We report on our experiences with using massively parallel sequencing of a targeted gene panel of 355 genes for investigating the genetic etiology of eight patients with a wide range of phenotypes including DD/ID, congenital anomalies and/or autism spectrum disorder. Targeted sequence enrichment was performed using the Agilent SureSelect Target Enrichment Kit and sequenced on the Illumina HiSeq2000 using paired-end reads. For all eight patients, 81–84% of the targeted regions achieved read depths of at least 20×, with average read depths overlapping targets ranging from 322× to 798×. Causative variants were successfully identified in two of the eight patients: a nonsense mutation in the ATRX gene and a canonical splice site mutation in the L1CAM gene. In a third patient, a canonical splice site variant in the USP9X gene could likely explain all or some of her clinical phenotypes. These results confirm the value of targeted MPS for investigating DD/ID in children for diagnostic purposes. However, targeted gene MPS was less likely to provide a genetic diagnosis for children whose phenotype includes autism.

Down syndrome in diverse populations

Down syndrome is the most common cause of cognitive impairment and presents clinically with universally recognizable signs and symptoms. In this study, we focus on exam findings and digital facial analysis technology in individuals with Down syndrome in diverse populations. Photos and clinical information were collected on 65 individuals from 13 countries, 56.9% were male and the average age was 6.6 years (range 1 month to 26 years; SD = 6.6 years). Subjective findings showed that clinical features were different across ethnicities (Africans, Asians, and Latin Americans), including brachycephaly, ear anomalies, clinodactyly, sandal gap, and abundant neck skin, which were all significantly less frequent in Africans (P < 0.001, P < 0.001, P < 0.001, P < 0.05, and P < 0.05, respectively). Evaluation using a digital facial analysis technology of a larger diverse cohort of newborns to adults (n = 129 cases; n = 132 controls) was able to diagnose Down syndrome with a sensitivity of 0.961, specificity of 0.924, and accuracy of 0.943. Only the angles at medial canthus and ala of the nose were common significant findings amongst different ethnicities (Caucasians, Africans, and Asians) when compared to ethnically matched controls. The Asian group had the least number of significant digital facial biometrics at 4, compared to Caucasians at 8 and Africans at 7. In conclusion, this study displays the wide variety of findings across different geographic populations in Down syndrome and demonstrates the accuracy and promise of digital facial analysis technology in the diagnosis of Down syndrome internationally.

Spinocerebellar Ataxia in Singapore: Predictive Features of a Positive DNA Test?

Significant differences in frequency of the different spinocerebellar ataxia (SCA) subtypes have been described to occur in different populations. A ‘blunderbuss’ diagnostic DNA testing approach would entail unnecessary healthcare cost. In this study, we determine the prevalence of SCA subtypes and predictive features of a positive DNA test in consecutive clinically diagnosed SCA cases in Singapore. Twenty-one consecutive patients from 14 families were evaluated over a 3-year period. Thirteen patients (61.9%) from 6 families had a positive DNA test. Eleven of these (all ethnic Chinese) had SCA 3 (abnormal CAG size ranged from 61 to 71), and 2 ethnic Malays had SCA 2 (abnormal CAG size of 39). Clinical features which were highly predictive of a positive DNA SCA test in our population included presence of a positive family history, chorea and dystonia, muscle and tongue fasciculations, gaze-evoked nystagmus, and hypertonia. Our study draws attention to the observation that knowledge of relatively specific features of the most common SCA subtype in a local population can greatly enhance the practical accuracy of the choice of which SCA DNA test to order.

An Additional Case of the Recurrent 15q24.1 Microdeletion Syndrome and Review of the Literature

We report a 9-year-old girl with 3 Mb interstitial deletion of chromosome 15q24 identified by oligonucleotide array comparative hybridization. She is of Chinese ancestry and shared some typical features of previously reported 15q24 deletion cases such as mild dysmorphism with developmental and speech delay. She also had mild hearing loss that was reported in one other case. We compared all 19 cases that are identified from array-CGH. The deletion occurred within an 8.3 Mb region from 15q23 to 15q24.3. The minimum overlapping deleted region is less than 0.5 Mb from 72.3 Mb to 72.7 Mb. The functions of the nine annotated genes within the region and how they might contribute to the microdeletion phenotype are discussed.

De novo 3q22.1 q24 deletion associated with multiple congenital anomalies, growth retardation and intellectual disability.

We describe a boy with a de novo deletion of 15.67 Mb spanning 3q22.1q24. He has bilateral micropthalmia, ptosis, cleft palate, global developmental delay and brain, skeletal and cardiac abnormalities. In addition, he has bilateral inguinal hernia and his right kidney is absent. We compare his phenotype with seven other patients with overlapping and molecularly defined interstitial 3q deletions. This patient has some phenotypic features that are not shared by the other patients. More cases with smaller deletions defined by high resolution aCGH will enable better genotype-phenotype correlations and prioritizing of candidate genes for the identification of pathways and disease mechanisms.

An anemic patient with phenotypical β‐thalassemic trait has elevated level of structurally normal β‐globin mRNA in reticulocytes

Of the numerous β‐thalassemic mutations linked or unlinked to the β‐globin gene, all invariably cause a decrease in or an absence of structurally normal β‐globin mRNA when assayed. Here we report an anemic patient with an elevated α‐/β globin synthesis ratio of 2.0 in his reticulocytes. The patients blood film showed marked red cell anisopoikilocytosis, microcytosis, and hypochromia, consistent with a typical β‐thalassemic trait phenotype. Acid‐eluted erythrocytes contained numerous Heinz bodies. Molecular analysis of the patients reticulocyte mRNA indicated that, compared to normal controls, there was a 3‐fold elevation of β‐globin mRNA when assayed by RT‐PCR and a 1.5‐fold elevation of β‐globin mRNA when assayed by RNA slot blotting. The level of α‐globin mRNA was normal when compared to that of normal adult controls. Extensive structural analysis of the β‐globin mRNA and gene by sequencing of RT‐PCR and PCR products, respectively, did not detect any mutations. Tryptic mapping of purified β‐globin chains also did not show any abnormal tryptic fragments. These data indicated that a relative insufficiency of structurally normal β‐globin mRNA was not a cause of this β‐thalassemic phenotype. Therefore, the lesion that caused this particular thalassemic phenotype is not linked to the β‐globin allele. Am. J. Hematol. 65:243–250, 2000.