A new form of hereditary persistence of fetal hemoglobin in blacks and its association with sickle cell trait.

A new form of hereditary persistence of fetal hemoglobin (HPFH) producing 3%-8% Hb F in heterozygotes and an elevation of F-cell counts as measured by both the Kleihauer test and an antibody fluorescent procedure was found during the study of a black family. Individuals with this anomaly also had sickle cell trait. A sickle cell homozygote who had apparently inherited the HPFH determinant had 20.3% Hb F. Both types of gamma-chains were present in equal proportions in the Hb F of these individuals. A population study revealed other AS individuals with increased Hb F synthesis, three of whom were sibs. The presence of this previously unrecognized form of HPFH might explain the mild clinical manifestations and the hemoglobin phenotypes of sickle cell homozygotes with unusual elevations of Hb F.