About Anemia
Anemia, one of the more common blood disorders, occurs when the level of healthy red blood cells (RBCs) in the body becomes too low. This can lead to health problems because RBCs contain hemoglobin, which carries oxygen to the body's tissues. Anemia can cause a variety of complications, including fatigue and stress on bodily organs.

Anemia can be caused by many things, but the three main bodily mechanisms that produce it are:

excessive destruction of RBCs
blood loss
inadequate production of RBCs
Among many other causes, anemia can result from inherited disorders, nutritional problems (such as an iron or vitamin deficiency), infections, some kinds of cancer, or exposure to a drug or toxin.

Anemia Caused by Destruction of RBCs
Hemolytic anemia occurs when red blood cells are being destroyed prematurely. (The normal lifespan of RBCs is 120 days; in hemolytic anemia, it's much shorter.) And the bone marrow (the soft, spongy tissue inside bones that makes new blood cells) simply can't keep up with the body's demand for new cells. This can happen for a variety of reasons. Sometimes, infections or certain medications — such as antibiotics or antiseizure medicines — are to blame.

In autoimmune hemolytic anemia, the immune system mistakes RBCs for foreign invaders and begins destroying them. Other kids inherit defects in the red blood cells that lead to anemia; common forms of inherited hemolytic anemia include sickle cell anemia, thalassemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and hereditary spherocytosis.

Sickle cell anemia is a severe form of anemia found most commonly in people of African heritage, although it can affect those of Caucasian, Saudi Arabian, Indian, and Mediterranean descent. In this condition, the hemoglobin forms long rods when it gives up its oxygen, stretching red blood cells into abnormal sickle shapes. This leads to premature destruction of RBCs, chronically low levels of hemoglobin, and recurring episodes of pain, as well as problems that can affect virtually every other organ system in the body. About 1 out of every 625 African-American children is born with this form of anemia.
Thalassemia, which usually affects people of Mediterranean, African, and Southeast Asian descent, is marked by abnormal and short-lived RBCs. Thalassemia major, also called Cooley's anemia, is a severe form of anemia in which RBCs are rapidly destroyed and iron is deposited in the skin and vital organs. Thalassemia minor involves only mild anemia and minimal red blood cell changes.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency most commonly affects males of African heritage, although it has been found in many other groups of people. With this condition the RBCs either do not make enough of the enzyme G6PD or the enzyme that is produced is abnormal and doesn't work well. When someone born with this deficiency has an infection, takes certain medicines, or is exposed to specific substances, the body's RBCs suffer extra stress. Without adequate G6PD to protect them, many red blood cells are destroyed prematurely.
Hereditary spherocytosis is a genetic disorder of the RBC's membrane that can cause anemia, jaundice (yellow-tinged skin), and enlargement of the spleen. The RBCs have a smaller surface area than normal red blood cells, which can cause them to break open easily. A family history increases the risk for this disorder, which is most common in people of northern European descent but can affect all races.

By : KidsHealth