Possible causes of hemolytic anemia

Genetic

This condition can be caused by some red cell membrane abnormalities such as hereditary spherocytosis or elliptocytosis.
It can also be caused by some hemoglobin abnormalities such as sickle cell anaemia or thalassaemia. Some enzyme defects such as Glucose-6-phosphate dehydrogenase and pyruvate kinase deficiency can also be the underlying disorder.

Immune

Isoimmune:

• haemolytic disease of newborn
• blood transfusion reaction

Autoimmune:

• Warm antibody type: idiopathic, SLE, lymphoma, chronic lymphatic leukemia, Evans' syndrome.
• Cold antibody type: cold haemagglutinin disease, paroxysmal cold haemoglobinuria, mycoplasma pneumonia, lymphoma, infectious      mononucleosis or other viral infections, chronic lymphatic leukemia.
• Drug related: drug absorbed onto red cell surface, e.g. penicillin, cephalosporins, or immune complex mediated, e.g. sulphonamides, quinidine.

Other causes:

• Non-immune
• trauma,
• cardiac haemolysis,
• micro-angiopathic anaemia
• haemolytic uraemic syndrome
• thrombotic thrombocytopenic purpura
• infection
• hypersplenism - enlarged lien
• membrane disorders,
• paroxysmal nocturnal haemoglobinuria,
• liver diseases

Excessive blood loss may also occur over a long period of time (chronic bleeding):

• Heavy menstruation
• Bleeding cancer or polyps in the gut
• Bleeding gastric or duodenal ulcers
• Nosebleeds
• Bleeding hemorrhoids

Mechanism and course of the disease

Hemolytic anemia occurs when the bone marrow is unable to compensate premature destruction of red blood cells by increasing their production.  Red blood cells are being destroyed by autoantibodies. This may occur suddenly, or it may develop gradually. In some people, the destruction may stop after a period of time while in other people, it persists and becomes chronic. What triggers these antibodies to attack these red blood cells is still unknown. Haemolysis may occur by two mechanisms:

Intravascular

This type occurs most commonly due to complement fixation, trauma, or other extrinsic factors. The most common triggers are:

• prosthetic cardiac valves,
• glucose-6-phosphate dehydrogenase deficiency,
• thrombotic thrombocytopenic purpura,
• disseminated intravascular coagulation
• paroxysmal nocturnal haemoglobinuria
• Extravascular

The red blood cells are removed from the circulation by the mononuclear-phagocytic system either because they are defective or there is the presence of bound immunoglobulins on their surfaces.

The etiology of premature erythrocyte destruction is diverse and can be caused by conditions such as:

• intrinsic membrane defects,
• abnormal hemoglobins,
• erythrocyte enzymatic defects,
• immune destruction of erythrocytes,
• mechanical injury,
• hypersplenism