Cd denotes all genotypes containing at least one sickle gene, In which hb makes up at least half the haemoglobin present. Major sickle genotypes described so far include the following hbbss disease or sickle cell anemia the most frequently encountered form, Homozygote for the s globin with usually a severe or moderately severe phenotype and with the shortest survival hbs/b, 0 thalassemia, Double heterozygote for hbs and b, 0 thalassemia, Clinically indistinguishable from sickle cell anemia sca hbs/b, Thalassemia, Mild, To, Moderate severity with variability in different ethnicities hbsc disease, Double heterozygote for hbs and hbc characterized by moderate clinical severity hbs/hereditary persistence of fetal hb s/hphp, Very mild or asymptomatic phenotype hbs/hbe syndrome, Very rare with a phenotype usually similar to hbs/b, Thalassemia rare combinations of hbs with other abnormal hemoglobins such as hbd los angeles, G, Philadelphia, Hbo arab, And others