In many persons there is a mild hypochromic microcytic anemia, with slight jaundice and splenomegaly. Most individuals with Thalassemia minor however, have no symptoms or abnormal physical signs. Usually there is no anemia. RBC count is elevated, hemoglobin and hematocrit are reduced. The mean cell hemoglobin concentration is low but often normal.
Osmotic fragility is decreased.
The serum iron concentration is normal or high, and the serum ferretin level is normal. It is interesting to note that geographic areas with the highest frequency of sickle cell gene is also areas where infection with plasmodium malaria is common. This correlation strongly suggest that Hgb S confers some sort of selective advantage against fatal malarial infections. By this mechanism the gene frequently probably builds up. In Hgb S the glutamic acid in 6th position on the beta chain is replaced by Valine.