Hb seal rock [(α2)142 term→Glow, Codon 142 TAA→GAA]: An extended α chain variant associated with Anemia, Microcytosis, and α-Thalassemia-2 (- 3.7 Kb)^a

Hb Seal Rock was first reported in a young African-American woman and her 2-year-old daughter (1). It is an extended a chain variant which, like Hb Constant Spring, is present in small quantity and is expressed as an α- Hb H disease was observed in the index case with Hb Pakse. In that case, however, the genotype of the proband was α(Pakse)α/- -, inasmuch as she had the SEA α-thal-1 deletion on one chromosome 16 and the α2-Pakse mutation on the other. In another family in which Hb Pakse, Hb Constant Spring, and the -3.7 kb α-thal-2 gene occurred, it was observed that the combinations α(Pakse)α/α and α(Pakse)α/α(-3.7 kb) were both associated with mild anemia and only slight microcytosis (27). The expected gradation in severity of anemia and microcytosis is well exemplified in these three complementary studies (Table IV).