1. Geographic, clinical and genetic data of 35 new cases of microdrepanocytic disease are presented.
2. These data suggest that sickle cell trait and microdrepanocytic disease are not infrequent in the eastern district of Sicily, perhaps with some small foci of sicklemic subjects.
3. The clinical history of adult patients and the personal examination of some cases of microdrepanocytic disease in children show the existence of mild forms of the disease and of forms appearing late in life.
4. From the clinical viewpoint, this series shows several interesting findings in the patients with microdrepanocytic disease: painful osteoarticular crises are inconstantly present; splenomegaly may undergo a spontaneous lessening during the course of the disease, analogous to that which occurs in sickle cell anemia; in women with microdrepanocytic disease miscarriages are frequent and successful pregnancies and births are extremely rare.
5. Hematologic studies reveal hypochromic anemia, leukocytosis, nucleated erythrocytes in the circulating blood, marked abnormalities in the morphology of the erythrocytes, and decreased cell fragility to hypotonic saline.
6. Genetic studies of the new cases again show the simultaneous presence in the patients with microdrepanocytic disease of the genes responsible for microcythemia and sickle cell trait.