causes condition has contributing genetic variation causes molecular phenotype Increased Hemoglobin F Hemoglobin S HBG1 and/or HBG2 Mutations Sickle Cell Disease-S/HPFH HBB, GLU6VAL SCD Genotype HBB, 106-KB DEL Hemoglobin Genotype S/HPFH S/HPFH Genotype SCDO (Clair Ingram) Request inclusion into relevant ontology None Haemoglobin Genotype S/HPFH Stamatoyannopoulos, G. (2005). Control of globin gene expression during development and erythroid differentiation. Experimental Hematology, 33(3), 259. http://doi.org/10.1016/j.exphem.2004.11.007 Genotype whereby a person is heterozygous for a hemoglobin S mutation and heterozygous for a mutation that causes persistant fetal hemoglobin production into adulthood. HPFH causative mutations are largely due to deletions in the beta-globin locus, but also by point mutations in the gamma-globin gene promoters.