SOD2 is an antioxidant protein that protects cells against mitochondrial superoxide. Hematopoietic stem cells (HSCs) lacking SOD2 are capable of rescuing lethally irradiated hosts, but reconstituted animals display a persistent hemolytic anemia characterized by increased oxidative damage to red cells, with morphologic similarity to human "sideroblastic" anemia. We report further characterization of this novel SOD2-deficiency anemia. Electron micrographs of SOD2-deficient reticulocytes reveal striking mitochondrial proliferation and mitochondrial mem-

While a family history of breast cancer in first-degree relatives is an important risk factor for breast cancer, gathering information such as the age at diagnosis of affected relatives or information on second-degree relative history may be unnecessary in assessing personal breast cancer risk among women age >or=40 years.