Concomitant inheritance of alpha-thalassemia in beta 0- thalassemia/Hb E disease.

Concomitant inheritance of alpha-thalassemia in patients with beta 0-thalassemia/hemoglobin (Hb) E disease was detected by restriction endonuclease DNA mapping. Among 42 patients with beta 0-thalassemia/Hb E disease, seven were found to have an alpha-thalassemia-2 haplotype. Of these, five belonged to the rightward or 3.7-kb type of alpha-thalassemia-2 and the remaining two the leftward or 4.2-kb type. All the seven patients with alpha-thalassemia-2 haplotype had hemoglobin levels of 7.4 g/dl or above; those without detectable alpha-thalassemia had hemoglobin levels both higher and lower than 7.4 g/dl. The latter attended the clinic regularly, the former did occasionally. These findings suggest that concomitant inheritance of alpha-thalassemia can alleviate the severity of beta 0-thalassemia/Hb E disease. Failure to find alpha-thalassemia-1 haplotype in these patients suggests that concomitant inheritance of alpha-thalassemia-1 with beta 0-thalassemia/Hb E might lead to so mild a condition that the individuals do not present clinically. The fact that many patients without a detectable alpha-thalassemia haplotype also had hemoglobin levels of 7.4 g/dl or higher suggests that there are additional factors responsible for the mildness of beta 0-thalassemia/Hb E disease.