causes condition has contributing genetic variation causes molecular phenotype Sickle Cell Disease-SD Hemoglobin S Hemoglobin D HBB, GLU6VAL SCD Genotype Hemoglobin Genotype SD Haemoglobin Genotype SD None SD Genotype SCDO Compound heterozygous inheritance of Hb S and Hb D mutations. Hb S occurs from substitution of valine for glutamic acid in the beta-6 position (beta6Glu>Val). Hb D generally results from substitution of glutamic acid for glutamine at beta-121 (beta121Glu>Gln); such as the Hb D-Punjab/Hb D-Los Angeles variants. There are several other Hb D variants, including Hb D-Iband where threonine is substituted by lysine at beta-87 (beta87Thr>Lys) and Hb D-Iran where glutamic acid is substituted by glutamine at beta-22 (beta22Glu>Gln). Request inclusion into relevant ontology HBB, SER9TYR HBB, GLU121GLN HBB, GLY16ARG HBB, ASN19LYS HBB, GLU22GLN HBB, GLU22VAL HBB, THR87LYS HBB, GLU121ALA