The Sickle ß-Thalassemia Phenotype.

Sß-thalassemia (Sß-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 Sß-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 Sß-thal patients were also screened for the HBG2 Xmn-1 polymorphism. ß-Thal mutations were determined by arrayed primer extension or direct sequencing. There were 70 SS and 32 Sß-thal patients with mean ages of 14.8±5.9 and 14.2±5.9 years, respectively. The Sß-thal patients had more frequent, severe pain episodes per year compared with the SS, while the patterns among Sß-thal and Sß-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 Sß-thal patients. However, none of the Sß-thal patients had been transfused. Among the Sß-thal patients, 25 had ß-thal and 7 had ß-thal mutations, the most common being cd39 (C→T) and IVS-I-110 (G→A), respectively. Sß-thal shows a severe phenotype in Kuwait, even among those with Sß-thal, in whom the IVS-I-110 (G→A) mutation is predominant.