Abstract
1. A brief review is presented of the genetic theories of sickle cell anemia and the sickle cell trait.
2. The genetic data on 2 families of asymptomatic individuals with the sickle cell trait and of 3 families of patients with sickle cell anemia are reported. These data confirm the heterozygous-homozygous theory of Neel.
3. The possibility is considered that many of the cases of sickle cell anemia described in the white race are actually examples of "microdrepanocytic disease."
4. Microdrepanocytic disease is a new syndrome, first described by the authors from Italy. It has some of the characteristics of both sickle cell anemia and Mediterranean anemia. On the basis of studies in 11 families, the presence of the sickle cell trait in one parent and of microcythemia (Mediterranean anemia trait) in the other, results in microdrepanocytic disease in some of the offspring. Hematologic studies in these patients indicate the simultaneous presence of both sickle cell and microcythemic genes.
5. Genetic studies of these families suggests that the genes for microcythemia and for sicklemia are located on different chromosomes and are inherited independently of each other. On the other hand, their simultaneous presence leads to a disease of a moderate degree of severity having many of the features of sickle cell anemia.
