Anaemia is defined as the decrease in the RBC number, hematocrit or the hemoglobin level as per the age, sex and the altitude at which the patient resides. Anaemia results from the reduction in the oxygen carrying capacity of the blood and results in the symptoms developed due to the reduced oxygen supply of the organs.
Anaemia can be divided based upon the etiology, morphology and the clinical presentation.
Based upon the cause, anaemia develops either due to blood loss, increased destruction or decreased production. The Blood loss could be acute as in trauma( Concealed hemorrhage as in blunt abdominal or chest injuries and revealed hemorrhage as in road traffic accidents), in the post operative period following a major surgery, or acute obstetric blood loss as in ectopic pregnancy, incomplete abortion or in postpartum hemorrhage. Most of these cases present as SHOCK rather than anaemia and require active intervention with IV fluid. Moderate amount of loss can lead to anaemia.
Chronic Blood loss is most commonly seen with GI ulcerations , parasitic infestation most commonly hookworm, and abnormal menstrual bleeding like polymenorrhagia.
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| Classification of Anaemia based on etiology. |
Hemolysis is either due to intracellular cause or extracellular cause. The cellular cause generally leads to abnormal RBC which are easily sequestered in Spleen and hence destroyed. All the membrane defects either acquired (Paroxysmal Nocturnal Hemoglobinuria) or congenital (Spherocytosis or ovalocytosis), Enzyme defect (G6PD deficiency), Hemoglobinopathies (Thalassemia spectrum of disease).
Extracellular causes could be autoagglutination as seen in transfusion related ABO incompatibility or Rh incompatibility seen in Erythroblastosis fetalis. Autoimmune diseases such as SLE, RA, malignancy, drugs, mycoplasma infection can cause hemolysis. Other extracellular causes include
mechanical trauma, Infections like malaria, lead poisoning, Viper venom, and sequestration seen in Hypersplenism can cause hemolysis.
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| Classification of hemolytic anemia |
The decrease production of RBC is either genetic defect as seen in thalassemia or fanconi an anemia,
nutritional deficiency of iron, vitamins and proteins. Deficiency of erythropoeitin seen in renal failure, and anaemia of chronic illness. Leukemia has pancytopenia, and space occupying lesions in marrow restrict RBC growth. parvovirus b19 and chronic infection as well cause anaemia.
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| Causes of decreased production of RBC. |
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