Anemia is a lower than normal number of red blood cells (erythrocytes) in the blood, usually measured by a decrease in the amount of hemoglobin. Hemoglobin is the red pigment in red blood cells that transports oxygen. Anemia can be temporary or long-term. It can range from mild to severe.

a rare immunological disorder characterized by the virtual absence of gamma globulin in the blood and consequent susceptibility to infection