Anemia

anemia, condition in which the red bloodexternal link, opens in a new tab cells (erythrocytesexternal link, opens in a new tab) are reduced in number or volume or are deficient in hemoglobinexternal link, opens in a new tab, their oxygen-carrying pigment. The most noticeable outward symptom of anemia is usually pallor of the skin, mucous membranes, and nail beds. Symptoms of tissue oxygenexternal link, opens in a new tab deficiency include pulsating noises in the ear, dizziness, fainting, and shortness of breath. Compensatory action of the heart may lead to its enlargement and to a rapid pulse rateexternal link, opens in a new tab. There are close to 100 different varieties of anemia, distinguished by the cause and by the size and hemoglobin content of the abnormal cells.