Anemia & Types of Anemia and Their Causes

Anemia, one of the more common blood disorders, occurs when the number of healthy red blood cells decreases in the body. The disc-shaped red blood cells contain hemoglobin, a unique molecule that carries oxygen to the body's tissues.   

Anemia occurs for different reasons. These include:   

• increased destruction (break down) of red blood cells (RBCs)
• increased blood loss from the body
• inadequate production of red blood cells by the bone marrow   

In some cases anemia results from an inherited disorder, whereas in other cases the condition is caused by something in a person's environment, such as a nutritional problem, infection, or exposure to a drug or toxin. 

Types of Anemia and Their Causes

 
Anemia Caused by Destruction of Red Blood Cells
Hemolytic ("hemo" means blood, "lytic" means destroying) anemia .

 occurs when red blood cells are being destroyed prematurely and the bone marrow (the soft, spongy tissue inside bones that produces 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 a condition known as autoimmune hemolytic anemia, the immune system mistakes red blood cells for foreign invaders and begins destroying them. Other children inherit defects in the red blood cells, which may involve the RBC's structure or the production of hemoglobin or RBC enzymes. Common forms of inherited hemolytic anemia include sickle cell anemia, thalassemia, and glucose-6-phosphate dehydrogenase deficiency.  

Sickle cell anemia 

is a severe form of anemia found almost exclusively in people of African heritage, although it may also 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 results in premature destruction of red blood cells, chronically low levels of hemoglobin, and recurring episodes of pain. About one out of every 500 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 red blood cells. Thalassemia major, also called Cooley's anemia, is a severe form of anemia in which red blood cells 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 men of African heritage, although it has been found in many groups of people. The red blood cells of people with this condition either do not make enough of the enzyme G6PD or the enzyme that is produced is abnormal and does not work well. When someone born with the deficiency has an infection, takes certain medicines, or is exposed to specific substances, the body's red blood cells suffer extra stress. Without adequate G6PD to protect them, many red blood cells are destroyed prematurely.

Anemia Caused by Blood Loss
 
Blood loss can also cause anemia - whether it's because of excessive bleeding due to injury, surgery, or a problem with the blood's clotting mechanism. Slower, long-term blood loss, such as intestinal bleeding due to inflammatory bowel disease, can also cause anemia. Anemia can also result from heavy menstrual periods in teen girls and women. Any of these factors will also increase the body's need for iron because iron is needed to make new red blood cells.

Anemia Caused by Inadequate RBC Production
Infants are born with high levels of hemoglobin and RBCs in their blood. This occurs in the fetus to help fetal blood carry enough oxygen while the developing baby is in the relatively oxygen-poor environment inside the uterus. After birth, when more oxygen is available, the baby's hemoglobin level normally drops to a low point at about 2 months of age, a condition known as physiologic anemia of infancy. After this occurs, the infant's body gets the signal to increase RBC production. This temporary and expected drop in the blood count is considered normal and no treatment is needed.

Anemia also occurs when the body isn't able to produce enough healthy red blood cells. This can happen because of a deficiency of iron or certain other substances in the body or from inherited defects or diseases that interfere with the production of red blood cells.  

Iron is essential for the production of hemoglobin in red blood cells. Poor dietary iron intake (or excessive loss of iron from the body) leads to iron-deficiency anemia, the most common cause of anemia in children. Iron-deficiency anemia can affect children at any age, but it is most commonly seen in children under 2 years of age, and in teens, particularly in adolescent girls who have started menstruating.

During the first 6 months of life, babies are usually protected against developing iron deficiency due to the stores of iron built up in their bodies while they are in the uterus. However, by the second half of the first year of life, as infants continue to undergo significant growth, often they do not take in enough iron through breast milk alone or regular cow's milk (which contains less iron than fortified infant formula) to meet their iron needs. Regular cow's milk can also cause some infants to lose iron from their intestines, and drinking lots of it can make an infant less interested in eating other foods that are better sources of iron. For these reasons, regular cow's milk is not recommended for children until they reach 1 year of age and are eating an iron-rich diet.

The growth spurt that occurs during puberty is also associated with an increased risk of iron-deficiency anemia. Girls are at particularly high risk because of the onset of menstruation; the monthly blood loss increases the need for dietary iron. In a recent report on iron deficiency in the United States, the Centers for Disease Control and Prevention (CDC) noted that, according to a 1996 survey, less than half of 1- to 2-year-olds and just over one fourth of teen girls were meeting the recommended daily intake of iron.  

Anemia can be caused by deficiency in the nutrients folic acid and vitamin B12, both of which are necessary for normal blood production. 

Pernicious anemia 

is a type of anemia that occurs when a person lacks a substance that is necessary to absorb and process vitamin B12. However, these forms anemia are rarely found in babies and young children.   

Aplastic anemia 

occurs when the bone marrow is unable to produce sufficient numbers of blood cells. More often, aplastic anemia is caused by a virus infection or exposure to certain toxic chemicals, radiation, or medications, such as antibiotics, antiseizure medications, or cancer medications. Some childhood cancers can cause anemia of this type, such as with certain types of leukemia in which abnormal cells crowd out the bone marrow cells needed to produce blood cells. Chronic diseases of other organs can result in anemia. For example, the kidneys and thyroid gland make hormones that are needed by the bone marrow to produce blood cells.

Signs and Symptoms of Anemia
The most common sign of iron deficiency and other types of nutritional anemia is mild paleness of the skin, along with decreased pinkness of the lips, the lining of the eyelids, and the nail beds. A friend or relative who sees your child only occasionally may be more likely to notice this than you because the changes usually happen so gradually.

Other common signs of anemia may include:

• irritability
• fatigue
• dizziness, lightheadedness, and a rapid heartbeat

Depending on the condition causing the anemia, other signs and symptoms may occur, such as jaundice (yellow-tinged skin), dark tea-colored urine, easy bruising or bleeding, and enlargement of the spleen or liver.

In infants and preschool children, iron-deficiency anemia can result in developmental delays and behavioral disturbances, such as decreased motor activity and problems with social interaction and attention to tasks. Recent research studies indicate that behavioral problems may persist into and beyond school age if the iron deficiency is not properly treated.  

Diagnosing Anemia
In many cases, doctors don't discover anemia until they run blood tests as part of a routine physical examination. A complete blood count (CBC) may indicate that there are fewer red blood cells than normal. Other diagnostic tests may include:

• Blood smear examination: Microscopic examination of red blood cells after blood is smeared on a glass slide can sometimes indicate the cause of the anemia.
• Iron tests: These include total serum iron and ferritin tests, which can help to determine whether anemia is due to iron deficiency.
• Hemoglobin electrophoresis: This test identifies various abnormal hemoglobins in the blood and is used to diagnose sickle cell anemia and the thalassemias.
• Bone marrow aspiration and biopsy: This test can help determine whether cell production is happening normally in the bone marrow. It's the only way to diagnose aplastic anemia definitively and is also used if it is suspected that a disease affecting the bone marrow (such as leukemia) could be the cause for the anemia.

In addition to running these tests, your child's doctor may ask about a family history of anemia and your child's symptoms and medications. This may lead the doctor to perform other tests to look for specific diseases that might be the underlying cause of the anemia.