No abstract

Summary. Globin synthesis was studied in three Jamaican Negro families with 18 heterozygotes and five homozygotes for β‐thalassaemia. Synthesis of the β‐chain of Hb A in the peripheral blood of heterozygotes was equal to that of α‐chain in 10 patients and was decreased in the remainder. In one patient with Hb C β‐thalassaemia, the β/α ratio was normal. These findings were similar to those in American Negroes, but differed from those in Caucasians with β‐thalassaemia trait, in each of whom the β/α ratio was decreased. Globin synthesis was balanced in the bone marrows of Negro and Caucasian heterozygotes. Despite the milder clinical disease in Negro homozygotes as compared to Caucasian patients, the β/α synthesis ratios were similar in both groups. The presence of α‐thalassaemia combined with β‐thalassaemia in Negro heterezygotes is not a likely explanation for the high incidence of balanced globin synthesis ratios. The expression of relative β‐ to α‐chain synthesis in Negro heterozygotes appears to be modified by a factor which is not linked to the δ‐chain locus. The nature of this factor is not known at present.

Globin synthesis was studied in four Negro families including 10 members with Hb A-HPFH and four with Hb S-HPFH. The beta/alpha specific activity ratios in 10 of these HPFH heterozygotes were similar to those of the control group. In two patients with Hb A-HPFH, the beta/alpha ratio was slightly decreased in one (0.84) and clearly decreased in another (0.78). In two of the patients with Hb S-HPFH the ratios were clearly decreased (0.71 and 0.75). The extended range of beta/alpha ratios in these 14 patients is similar to that of Negro patients with beta-thalassaemia trait. These studies indicate that a decreased beta/alpha ratio may be found in HPFH, as well as in beta-thalassaemia. Bone marrow globin synthesis was measured in two patients with Hb S-HPFH and decreased peripheral blood beta/alpha ratios, and in one with Hb A-HPFH and a normal peripheral blood beta/alpha ratio. In each patient the (beta+gamma)/alpha ratio of radioactivities as well as the beta/alpha specific activity ratio was close to 1 and therefore balanced, indicating more rapid decay of beta-chain synthesis relative to alpha-chain during red cell maturation or extremely rapid destruction of newly synthesized excess alpha-chains in the bone marrow.