Genotype-phenotype correlation in patients with deletional and nondeletional mutations of Hb H disease in Southwest of Iran

Revisiting and updating molecular epidemiology of α-thalassemia mutations in Thailand using MLPA and new multiplex gap-PCR for nine α-thalassemia deletion

α-thalassemia is an inherited blood disorder that is most frequently found in Southeast Asian populations. In Thailand, molecular characterization can diagnose most patients with α-thalassemia; however, several atypical patients are also observed in routine analyses. Here, we characterized α-thalassemia mutations among 137 Hemoglobin H (Hb H) disease patients and three fetuses of Hb Bart's hydrops, a fatal clinical phenotype of α-thalassemia. Specifically, we performed multiplex ligation-dependent probe amplification (MLPA) followed by direct DNA sequencing. We noticed common genotypes in 129 patients and eight patients had rare Hb H disease caused by compound heterozygous α0-thalassemia (--CR or --SA deletion) with α+-thalassemia (-α3.7/-α4.2/αConstant Springα). Furthermore, two affected fetuses had the --SA/--SEA and one had the --CR/--SEA genotypes. Next, we developed and validated a new multiplex gap-PCR and applied this method to 844 subjects with microcytic red blood cells (RBCs) from various parts of Thailand. The frequency of heterozygous α0-thalassemia was dominated by --SEA 363/844 (43%), followed by --THAI 3/844 (0.4%), --SA 2/844 (0.2%), and --CR 2/844 (0.2%) mutations. These findings suggest that aforementioned four mutations should be routinely applied to increase the effectiveness of diagnosis and genetic counseling in this region.

Gene Mutation Spectrum among Alpha-Thalassaemia Patients in Northeast Peninsular Malaysia

(1) Background: Alpha (α)-thalassaemia is a genetic disorder that affects 5% of the world population. Deletional or nondeletional mutations of one or both HBA1 and HBA2 on chromosome 16 will result in reduced production of α-globin chains, a component of haemoglobin (Hb) that is required for the formation of red blood cells (RBCs). This study aimed to determine the prevalence, haematological and molecular characterisations of α-thalassaemia. (2) Method: The parameters were based on full blood count, high-performance liquid chromatography and capillary electrophoresis. The molecular analysis involved gap-polymerase chain reaction (PCR), multiplex amplification refractory mutation system-PCR, multiplex ligation-dependent probe amplification and Sanger sequencing. (3) Results: With a total cohort of 131 patients, the prevalence of α-thalassaemia was 48.9%, leaving the remaining 51.1% with potentially undetected α gene mutations. The following genotypes were detected: -α^3.7/αα (15.4%), -α^4.2/αα (3.7%), --^SEA/αα (7.4%), α^CSα/αα (10.3%), α^Adanaα/αα (0.7%), α^{Quong Szeα}/αα (1.5%), -α^3.7/-α^3.7 (0.7%), α^CSα/α^CSα (0.7%), -α^4.2/α^CSα (0.7%), -^SEA/α^CSα (1.5%), -^SEA/α^{Quong Sze}α (0.7%), -α^3.7/α^Adanaα (0.7%), --^SEA/-α^3.7 (2.2%) and α^CSα/α^Adanaα (0.7%). Indicators such as Hb (p = 0.022), mean corpuscular volume (p = 0.009), mean corpuscular haemoglobin (p = 0.017), RBC (p = 0.038) and haematocrit (p = 0.058) showed significant changes among patients with deletional mutations, but not between patients with nondeletional mutations. (4) Conclusions: A wide range of haematological parameters was observed among patients, including those with the same genotype. Thus, a combination of molecular technologies and haematological parameters is necessary for the accurate detection of α-globin chain mutations.