Mild sickle-cell anaemia in Iran associated with high levels of fetal haemoglobin.

Sixteen subjects, with sickle-cell anaemia, all Iranians (ages 3 to 56 years), with very mild symptomatology are reported. Some of the subjects had been totally asymptomatic. Splenomegaly was noted in 9 cases. There was an increase in the mean level of fetal haemoglobin (18%); this is the probable explanation for the mild phenotype. In 29 subjects with sickle-cell trait, the level of HbF was also significantly raised as compared with normal (1-6% vs. 0-6%). The mechanism of increased synthesis of HbF is unknown. The findings are similar to those reported in the Shiite Moslems of Saudi Arabia suggesting that in these populations there is a genetically-determined ability to produce high levels of Hb F in the presence of the sickle-cell gene.