The Sickle β-Thalassemia Phenotype.

Sβ-thalassemia (Sβ-thal) is common among Gulf Arab patients with sickle cell disease, but the phenotype of this group had not been well-documented. We have studied a group of Kuwaiti patients and compared the phenotype in the homozygotes (SS) and Sβ-thal patients. Complete blood count, hemoglobin quantitation, serum bilirubin, and lactate dehydrogenase were determined with standard techniques. The patients were screened for α-globin genotype. The Sβ-thal patients were also screened for the HBG2 Xmn-1 polymorphism. β-Thal mutations were determined by arrayed primer extension or direct sequencing. There were 70 SS and 32 Sβ-thal patients with mean ages of 14.8±5.9 and 14.2±5.9 years, respectively. The Sβ-thal patients had more frequent, severe pain episodes per year compared with the SS, while the patterns among Sβ-thal and Sβ-thal patients were not significantly different. There were no differences in the frequencies of acute chest syndrome, gallstones, and blood transfusion in the SS and Sβ-thal patients. However, none of the Sβ-thal patients had been transfused. Among the Sβ-thal patients, 25 had β-thal and 7 had β-thal mutations, the most common being cd39 (C→T) and IVS-I-110 (G→A), respectively. Sβ-thal shows a severe phenotype in Kuwait, even among those with Sβ-thal, in whom the IVS-I-110 (G→A) mutation is predominant.