Anaemia
Anaemia is defined as the reduction in circulating red blood cell-mass below normal levels. It reduces the oxygen-carrying capacity of the blood, leading to tissue hypoxia. It is diagnosed by haemoglobin concentration. The WHO defines anaemia as a haemoglobin concentration < 13 g/dL for men and < 12 g/dL for women, but the normal ranges vary a bit from laboratory to laboratory.
Anaemias can be classified according to the morphology of the RBCs or according to the etiology.
Classification of anaemias according to morphology:
| Microcytic anaemia | Normocytic anaemia | Macrocytic anaemia | |
|---|---|---|---|
| MCV (fL) | < 80 | 80 – 100 | > 100 |
| Pathomechanism | Insufficient haemoglobin production | Increased RBC loss and/or decreased erythropoiesis | Insufficient RBC production and/or maturation, possibly due to defective DNA synthesis or DNA repair |
| Possible causes | Iron deficiency anaemia | Haemolytic anaemias: | Vitamin B12 deficiency |
| Anaemia of chronic disease (late phase) | Sickle cell anaemia | Folate deficiency | |
| Thalassaemia | G6PD deficiency | Certain drugs (phenytoin, sulfa drugs) | |
| Lead poisoning | Paroxysmal nocturnal haemoglobinuria | Fanconi anaemia | |
| Chronic blood loss | Hereditary spherocytosis | Liver disease | |
| Autoimmune haemolytic anaemia | Alcohol abuse | ||
| Microangiopathic haemolytic anaemia (TTP/HUS) | |||
| Macroangiopathic haemolytic anaemia | |||
| Non-haemolytic anaemias: | |||
| Acute blood loss | |||
| Aplastic anaemia | |||
| Anaemia of chronic disease (early phase) |
General features of anaemia
- Fatigue
- Pallor – especially of lips and conjunctiva
- Weakness
- Exercise intolerance
- Palpitations
- Tachycardia