Anemia is a red blood cell (RBC) disorder wherein the mass of circulating red blood cells is reduced. This may either be caused by:
Reduction in the mass of circulating RBCs directly affects the amount of oxygen being supplied to body tissues. The 6 types of anemia have widely been classified as deficiency anemias, intrinsic and extrinsic anemias.
Iron deficiency in the body is the most common cause of anemia. When iron levels are low, the body is unable to make the adequate number of functional hemoglobin (Hb) proteins; therefore each RBC has lesser Hb units. This leads to an adaptation called microcytic anemia in which the RBC size is smaller than normal to maintain the Hb concentration in each cell.
Patients usually present with typical symptoms listed above, which can grow severe if the condition is left untreated for a long period.
Iron deficiency anemia is commonly treated with oral iron supplements and a recommended diet high in iron (such as red meat, beans, green vegetables) and foods that enhance iron absorption (fruits and vegetables containing vitamin C).
Folate and B12 are important for the development of RBCs from precursors to their fully developed form. These deficiencies cause the body to produce abnormally large RBCs that cannot function effectively. It can also affect the nervous system over a long period.
Apart from the typical symptoms, patients may experience:
Hemolytic anemias are a group of RBC disorders in which RBCs are destroyed faster than they are synthesized. These can widely be classified and compared as intrinsic vs extrinsic hemolytic anemias.
Intrinsic hemolytic anemia is due to internal factors that cause RBC to break down, such as cell membrane defects, Hb defects, and enzyme deficiencies.
Hb defects include thalassemia and sickle cell disease, as discussed below.
Thalassemia is a type of microcytic (smaller RBC) anemia due to decreased synthesis of the globin protein chains of Hb. It is caused by an inherited genetic mutation in Hb synthesizing cells. This mutation can occur in any of the four genes involved in synthesizing alpha hemoglobin chains or in the two genes involved in beta hemoglobin chain synthesis.
Symptoms can range from silent to severe, depending on the degree of genetic mutation. If only one alpha gene is mutated, the person will be a silent carrier of a disease. Three mutated genes result in moderate to severe symptoms and four mutated genes result in stillbirth.
Moderate to severe forms of thalassemia require treatment. The following treatment options are currently available:
SCD is an example of normocytic hemolytic anemia (meaning there will be a regular-sized but reduced number of RBCs in circulation). Due to a single genetic mutation, RBCs that are usually biconcave disc-shaped will now sickle, resembling the shape of a scythe. This prevents the usually flexible RBCs from passing through minute, single-cell wide capillary beds, affecting oxygenation of deep tissues.
People with a single gene defect are sickle cell carriers and do not present with symptoms. Half of their RBCs might sickle while the other half remains unaffected, leading to no symptom presentation unless the body is under stress. Affected patients with dual genetic mutations will variably present with:
Extrinsic hemolytic anemias are due to external factors causing hemolysis; majorly, autoimmune destruction of RBCs. Perfect RBCs are produced in the bone marrow but are prematurely destroyed in the bloodstream or the spleen. Although there are many examples, therefore, we will discuss warm and cold hemolytic anemias under the category of auto-immune hemolytic anemias (AIHA).
Warm AIHA is caused by IgG autoantibody that binds to the RBC membrane for destruction in temperatures around 37°C. The primary cause may be idiopathic (unknown), but other secondary factors like medication, malignancies, autoimmune conditions, and viral infections can cause warm AIHA.
Warm AIHA causes extravascular hemolysis i.e. destruction of RBCs outside the blood vessels such as in the spleen, also causing mild enlargement of the spleen.
Severe warm AIHA is treated with glucocorticoids and splenectomy (removal of the spleen). Immunosuppressive treatment can also prove effective, considering the role of autoantibodies in the disorder.
Cold hemolytic anemia is caused by the IgM autoantibody that preferentially binds to RBCs at temperatures between 0°C and 5°C. It activates the complement pathway (a protein-mediated defense mechanism) and intravascular hemolysis i.e. destruction of RBCs inside the blood vessels. The disorder can occur idiopathically in the elderly or due to infections like pneumonia, mononucleosis (aka the kissing disease), and chickenpox.
Apart from the typical symptoms listed above, many people with cold hemolytic anemia experience pain and a blue tinge to the limbs from poor circulation in the extremities.
As cold AIHA has underlying causes, it is important to treat those disorders to keep the AIHA at bay. People with mild symptoms may not require treatment and can simply manage this condition by avoiding the cold. In severe cases, an RBC transfusion can be performed.
Although there are many different types of anemias and they may have numerous underlying causes, they commonly reveal similar symptoms. Anemia itself may be a symptom of an underlying disease, like warm AIHA present in leukemia. So, if you experience any of the symptoms mentioned above, you should contact your physician at your earliest.