whose activity is 10 to 25 percent of normal may suffer excessive bleeding after surgery, dental extractions or a major injury
Sickling in sickle cell anemia is caused by the presence of an abnormal form of hemoglobin that reduces the amount of oxygen the red cells can carry, and causes them to become sickle-shaped (74). The anemia is aggravated by any condition which increases the body's requirement for oxygen, e.g. vigorous exercise, mountain climbing, flying at high altitudes without sufficient oxygen, or illness.
Immune thrombocytopenic purpura is caused by infection with the human immunodeficiency virus (HIV) which causes AIDS, and also causes the production of antibodies which destroy platelets (756). Systemic lupus erythematosus also causes thrombocytopenia by producing antibodies against platelets.
Acute lymphocytic leukemia is the most common childhood cancer, accounting for 25 percent of all cancers in children under age 15, and most commonly affecting children between the ages of three and five (765).
Iron deficiency anemia is caused by blood loss in adults, or a diet low in iron in children (743). Blood loss can be sudden, e.g from an injury or a nose bleed, or chronic, as from a stomach ulcer or colon cancer. Menstrual bleeding may cause iron deficiency anemia in premenopausal women.
Compensatory mechanisms for anemia include increased blood cell production, production of megaloblstic red cells and the production of microcytic (very small) red blood cells (742-745).
Pernicious anemia is caused by a deficiency of vitamin B12 (745). This can be caused by inadequate absorption of vitamin B12 (cobalamin). The vitamin is found in meat and vegetables and is usually readily absorbed in the ileum. For B12 to be absorbed, it must be combined with intrinsic factor, a protein which is produced in the stomach and carries the vitamin through the intestinal wall into the bloodstream. In pernicious ...