The Rare α-Thalassemia-1 of Blacks is a ζ-Thalassemia-1 Associated with Deletion of All α- and ζ-Globin Genes

Restriction endonuclease mapping with α and ζ-globin gene probes showed differences between the α-thalassemia-1 (α-thal-1) condition in two patients with HbH disease. One patient had the rare black type of α-thal-1 together with α-thal-2 and HbS heterozygosities. The second patient was a Laotian child with HbE, Hb Constant Spring (α-thal-2), and α-thal-1 heterozygosities. The diagnoses were based on clinical, hematologic, and biochemical data. Whereas DNA fragments hybridizing to a ζ-probe were obtained from the Laotian type of α-thal-1, neither a nor ζ-gene fragments could be identified deriving from the black type of α-thal-1. Therefore, the black type of α-thal-1 is associated with a deletion of the entire ζ2-ψζ-ψα-α2-α1gene complex and can be considered a ζα-thal-1. It is likely that homozygosity for such a condition will lead to embryonic wastage, explaining the absence of hydrops fetalis in blacks.