Shoaib Al Zadjali

Forecasting Hemoglobinopathy Burden Through Neonatal Screening in Omani Neonates

To evaluate the incidence of hemoglobinopathies in Omani subjects and to forecast its future burden on health resources, we initiated a prospective neonatal screening program in two major cities of the Sultanate of Oman. Consecutive cord blood samples from a total of 7,837 neonates were analyzed for complete blood counts and for hemoglobin (Hb) profile by high performance liquid chromatography (HPLC). No case with Hb H (β4) was detected. We observed that the overall incidence of α-thalassemia (α-thal) was 48.5% [based on the presence of Hb Barts (γ4)] and the β-globin-related abnormalities accounted for 9.5% of the samples (4.8% sickle cell trait, 2.6% β-thal trait, 0.9% Hb E trait, 0.8% Hb D trait, 0.08% Hb C trait, 0.3% sickle cell disease and 0.08% homozygous β-thal). This is also the first large study to establish reference ranges of cord red blood cell (RBC) indices for Omani neonates.

T2* cardiovascular magnetic resonance in the management of thalassemia patients in Oman

Myocardial siderosis in thalassemia major remains the leading cause of death in developed countries despite the use of iron chelating agents over the past three decades. Once cardiac failure occurs, it is difficult to reverse, but early detection could result in a better prognosis through more

Warfarin pharmacogenetics: development of a dosing algorithm for Omani patients

The objective of our present study was to develop a warfarin dosing algorithm for the Omani patients, as performances of warfarin dosing algorithms vary across populations with impact on the daily maintenance dose. We studied the functional polymorphisms of CYP2C9, CYP4F2 and VKORC1 genes to evaluate their impact on the warfarin maintenance dose in an admixed Omani patient cohort with Caucasian, African and Asian ancestries. We observed a 64-fold inter-patient variability for warfarin to achieve stable international normalized ratio in these patients. Univariate analysis revealed that age, gender, weight, atrial fibrillation, deep vein thrombosis/pulmonary embolism and variant genotypes of CYP2C9 and VKORC1 loci were significantly associated with warfarin dose in the studied patient population. However, multiple regression model showed that only the atrial fibrillation, and homozygous CYP2C9 variant genotypes (*2/*3 and *3/*3) and VKORC1 GA and AA genotypes remained significant. A multivariate model, which included demographic, clinical and pharmacogenetic variables together explained 63% of the overall inter-patient variability in warfarin dose requirement in this microgeographically defined, ethnically admixed Omani patient cohort on warfarin. This locally developed model performed much better than the International Warfarin Pharmacogenetics Consortium (IWPC) model as the latter could only explain 34% of the inter-patient variability in Omani patients. VKORC1 3673G>A polymorphism emerged as the single most important predictor of warfarin dose variability, even in this admixed population (partial R2=0.45).

Warfarin Pharmacogenetics: Polymorphisms of the CYP2C9, CYP4F2, and VKORC1 Loci in a Genetically Admixed Omani Population

Abstract This is the first study to evaluate the spectrum and prevalence of dose-predictive genetic polymorphisms of the CYP2C9, CYP4F2 and VKORC1 loci together, in a geographically defined, ethnically admixed healthy adult Omani population sharing common lifestyle/environmental factors. Since the present-day Omani population is the result of an admixture of Caucasian, African and Asian ancestries, we compared the pharmacogenetic profile of these three loci in this population. Interestingly, the Omani pharmacogenetic profile, in terms of allele and genotype distribution, has values that are intermediate between Caucasians and African Americans, the African admixture further substantiated by the presence of the CYP2C9*8 allele. However, limitations and usefulness of such comparisons warrant caution, as the data from pharmacogenetic literature do not always represent bona fide population categories. Furthermore, definition of study population based on microgeographical scale would be more appropriate in pharmacogenetic research rather than the flawed racial, ethnic, or social categorizations since pharmacogenetic variation is clinal, and genetic influences will be further altered by lifestyle and environmental factors.

dRTA and hemolytic anemia: first detailed description of SLC4A1 A858D mutation in homozygous state

Mutations in the anion exchanger 1 (AE1) gene encoding the erythroid and kidney anion (chloride–bicarbonate) exchanger 1 may result in familial distal renal tubular acidosis (dRTA) in association with membrane defect hemolytic anemia. Seven children presenting with hyperchloremic normal anion gap metabolic acidosis, failure to thrive, and compensated hemolytic anemia were studied. Analysis of red cell AE1/Band 3 surface expression by Eosin 5′‐maleimide (E5M) was performed in patients and their family members using flow cytometry. Genetic studies showed that all patients carried a common SLC4A1 mutation, c.2573C>A; p.Ala858Asp in exon 19, found as homozygous (A858D/A858D) mutation in the patients and heterozygous (A858D/N) in the parents. Analysis by flowcytometry revealed a single uniform fluorescence peak, with the mean channel fluorescence (MCF) markedly reduced in cases with homozygous mutation, along with a left shift of fluorescence signal but was only mildly reduced in the heterozygous state. Red cell morphology showed striking acanthocytosis in the homozygous state [patients] and only a mild acanthocytosis in heterozygous state [parents]. In conclusion, this is the first description of a series of homozygous cases with the A858D mutation. The E5M flowcytometry test is specific for reduction in the Band 3 membrane protein and was useful in conjunction with a careful morphological examination of peripheral blood smears in our patient cohort.

The β-globin promoter -71 C>T mutation is a β+ thalassemic allele.

A novel β‐globin gene promoter (−71 C>T) nucleotide change was recently posted to the HbVar database (ID 2701) without precision on phenotype and ethnicity. We found the same change in compound heterozygosity with Hb S [β6(A3)Glu>Val] in an Omani family with almost equal expression of Hb A and Hb S. This suggested that the −71 C to T mutation may be a mild β‐thalassemic allele. Subsequent search found three other independent cases with the same atypical Hb A:Hb S ratio, further confirming the mild thalassemic feature of this mutation. In addition, molecular screening of a set of subjects (with only Hb A) with borderline Hb A2 or MCV values revealed the presence of −71 C>T change in heterozygous state, altogether assigning the mutation as a mild β+ thalassemic allele. In a region such as Oman, where several genetic conditions of the red blood cell coexist (α‐ and β‐thalassemia, Hb S, Hb D, Hb E) in significant frequencies, it is crucial to decipher the molecular basis of these atypical forms of β+ thalassemias, especially in a genetic counseling setting.

Thiamine responsive megaloblastic anemia: The puzzling phenotype

Thiamine responsive megaloblastic anemia (TRMA) is characterized by a triad of megaloblastic anemia, non‐type 1 diabetes mellitus and sensorineural deafness. Other clinical findings have been described in few cases. The SLC19A2 gene on chromosome 1q 23.3 is implicated in all cases with TRMA. Our aim is to discuss the clinical manifestations of all Omani children diagnosed with TRMA and determine genotype–phenotype relationship.

Severity ranking of non-deletional alpha thalassemic alleles: insights from an Omani family study

In an Omani family, four different alpha thalassemic alleles, one single‐gene deletional (−α3.7) and three non‐deletional forms (αTSaudi, αΔ5nt, and αΔG), interact in various combinations and result in two distinct hematological phenotypes, with and without HbH inclusions. After excluding the presence of potential genetic modifiers, viz associated β‐thalassemic alleles or functional alpha hemoglobin stabilizing protein (AHSP) polymorphisms, we observed that only the genetic combinations involving αTSaudi mutation are associated with HbH inclusions (a marker of degree of α/β‐chain imbalance) and high reticulocyte count (a marker of ongoing hemolysis). Overall, the αTSaudi mutation is associated with a more severe α‐globin deficiency than the other two (αΔ5nt and αΔG) non‐deletional α0 thalassemic mutations. The likely molecular explanation is that the compensatory increase in the linked α1 globin gene expression is much more compromised in cases with αTSaudi mutation.

Hb A2′ (Hb B2) in the Omani population and diagnostic significance

Hb A2′ [δ16(A13)Gly→Arg], also called Hb B2, is a δ-globin chain variant that has been identified in several populations of African origin or ancestry and is easily identifiable in alkaline acetate cellulose electrophoresis as doubling of the Hb A2 band. However, in high performance liquid chromatography (HPLC), commonly employed nowadays, it elutes in the S window. Over a period of 2 years at the Sultan Qaboos University Hospital, Muscat, Oman, we identified 25 Omanis with this variant. The quantity of Hb A2 ranged from 0.9 to 1.8% in heterozygotes and was undetectable in the single homozygous case. As both α- and β-thalassemia (α- and β-thal) as well as Hb S [β6(A3)Glu→Val] are common in the Omani population, it is important to be aware of the presence of Hb A2′ in this population to avoid misinterpretation of the HPLC data in terms of underdiagnosis of β-thal carriers and overestimation of α-thal based on Hb A2 levels in sickle cell carriers. The haplotype associated with Hb A2′ in Oman is identical to that described in African populations, suggesting a common origin for this mutation and its introduction into Oman by gene flow.

Hb Sheffield [β58(E2)Pro→His] in Oman: potential pitfall in genetic counseling.

A novel β-globin structural variant, namely Hb Sheffield [β58(E2)Pro→His], was recently found as a sporadic event in a British Subject and posted to the HbVar database (ID 2672). Here we describe the same variant in 11 Omani subjects in the heterozygous state and in one Omani woman in compound heterozygosity with Hb S [β6(A3)Glu→Val]. Hb Sheffield coelutes in the Hb A2 window in the high performance liquid chromatography (HPLC) system as does Hb E [β26(B8)Glu→Lys], and might be erroneously diagnosed as Hb E unless additional tests including DNA analyses are done. Indeed, correct diagnosis of Hb E is important because of its association with other β-thalassemic and variant alleles can result in relevant clinical conditions, while Hb Sheffield will not. In a genetic (premarital) counseling setting, and in regions where both Hb E ad Hb Sheffield are present, failure to distinguish these variants will represent a serious pitfall.