Types and causes of anaemia

Types and causes of anaemia

Types of anaemia

Of the many types of anaemia, the condition is typically broken down into three major type classifications. Anaemia is classified according to the size of RBCs in the body. This ultimately ties in with underlying causes, types and reasons for the malfunction.

The three main type classifications are:

  • Microcytic anaemia: RBCs are smaller than normal in size and are caused by low levels of iron in the system. This often results in conditions such as iron-deficiency anaemia and inherited disorders of haemoglobin, such as thalassemia.
  • Normocytic anaemia: RBCs are normal in size but are lacking in the number produced to replenish older cells ultimately excreted from the body. This type is commonly associated with chronic conditions such as kidney disease.
  • Macrocytic anaemia: RBCs are larger in size than is normal. Often, excessive alcohol consumption is an underlying factor and results secondary to conditions, such as pernicious anaemia. Macrocytic anaemia occurs when there is a deficiency of vitamin B12 or folate.

Anaemia medical diagram showing normal and abnormal blood cell count and human circulation in an artery or vein

What causes anaemia?

Essentially, anaemia is as a result of one of three things:

  • The body isn’t producing enough RBCs for healthy function (i.e. the body is lacking in RBC's and therefore has low haemoglobin)
  • RBCs are being lost (old cells) at a faster rate than they are being produced in the bone marrow, usually due to bleeding in the body
  • The body is actively destroying RBCs due to a deficiency or illness

From the type classifications and fundamental causes, anaemia can be broken down into more specifically labelled type groups.

Some of the main cause types include:

  • Iron-deficiency anaemia: An insufficient amount of iron in the body (sometimes due to an iron-poor diet, commonly seen in infants, young children, teens, vegetarians and vegans) causes a decreased production of RBCs. This type is common worldwide and is often diagnosed in women who experience heavy menstrual bleeding during their reproductive years, and others suffering bleeding from ulcers, cancer, haemorrhoids, gastritis or use of medications, such as aspirin and ibuprofen, and other over-the-counter pain relievers relievers (these cause anaemia by perpetuating gastritis or peptic ulcers). Bleeding during childbirth and sometimes multiple pregnancies (due to increased metabolic demands in the body) and breastfeeding (which may deplete a woman’s iron levels) can bring about anaemia as well. Those who donate blood frequently or place their bodies through endurance fitness training (endurance sports) may be at risk of this type of anaemia.
  • Vegetarian dietVitamin-deficiency anaemias: A lack of vitamin B-12 and folate can also hinder healthy RBC production. It may be that a person is not getting enough of these key nutrients in their diet or their body is having trouble processing these vitamins. Common variations of this type include pernicious anaemia (poor vitamin B-12 absorption), megaloblastic anaemia (deficiency in vitamin B-12 or folate, or both). Those who eat little or no meat in their diets may lack vitamin B-12 which can cause this type of anaemia. Vegetables which are overcooked or not consumed often enough can also lead to a deficiency of folate in the system. If pregnant and lacking folate (folic acid), a developing baby runs the risk of neural tube defects, such as spina bifida.
  • Chronic disease anaemia: Chronic diseases can also have an impact on the sufficient production of RBCs and by association then cause a type of anaemia. Conditions such as cancer, rheumatoid arthritis, HIV-AIDS, kidney disease, hypothyroidism, lupus, diabetes and Crohn’s disease are some that can interfere with the RBC production process.
  • Anaemia associated with bone marrow disease: Diseases that affect RBC production in the bone marrow include leukaemia and myelofibrosis. Cancer (metastatic cancer cells) and cancer-like conditions range from mild to life-threatening and cause malfunctions in the bone marrow that ultimately have a domino effect of deficiency throughout the body. Rare, but life-threatening, aplastic anaemia occurs when the body is incapable of producing enough RBCs. The condition typically occurs as a result of infections (such as hookworm), existing autoimmune diseases, exposure to toxic chemicals and as an adverse reaction to medications. The bone marrow may also be affected by exposure to lead, which is toxic for the system. Poisoning can lead to anaemia affecting the bone marrow’s normal functionality.
  • Haemolytic anaemias: This group type relates to a high number of RBCs that are destroyed at a faster rate than the bone marrow can replenish with new cells. This group type is often inherited, but can also develop at a later stage in life if a person falls ill with a blood disease that increases the RBC destruction rate, causing an imbalance. Also known as sickle cell disease, sickle cell anaemia is one such inherited condition that causes an irregularity in the way RBCs are formed. A defective form of haemoglobin causes the shape of cells produced to ‘sickle’ (creating a banana or crescent moon shape) instead of the normal round shape, which causes them to experience difficulty in travelling through the bloodstream. Often, these cells are prematurely destroyed which causes a chronic shortage of RBCs (both normal and sickle) in the bloodstream. Other underlying causes for haemolytic anaemias include infection stressors (snake or spider venom, infections or drugs, medications or condition treatments such as chemotherapy), toxins associated with advanced kidney or liver disease, vascular grafts, prosthetic heart valves, severe burns, tumours, exposure to chemicals, clotting disorders, severe hypertension and an enlarged spleen (rare).
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