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.

People with chronic anaemia develop compensatory mechanisms, which is why they can function with lower Hb.

Classification of anaemias according to morphology

Anaemias can be classified according to the morphology of the RBCs or according to the etiology.

	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