Abnormal Hemoglobin in SCD Abnormal Hemoglobin Sickling Hemoglobin with Two Beta-Globin Gene Substitutions None Request inclusion into the HPO, below "Abnormal Hemoglobin". A hemoglobin that sickles due to the presence of two beta-globin gene mutations within the same HBB gene. Doubly Substituted Sickling Hemoglobin