Anaemia
Anaemia is defined as a reduction in haemoglobin concentration below the normal range for the age and sex of the individual. It is usually accompanied by a reduction in red cell count and haematocrit.
Clinical features
Symptoms of anaemia are mainly shortness of breath on exertion, tiredness and headaches. If it is severe in older people, congestive heart failure or angina may develop. There is a rise in red cell 2,3-diphosphoglycerate (2,3-DPG) in most cases of anaemia so that oxygen is given up more readily to tissues. The main signs are pallor of the mucous membranes if the haemoglobin is <90 g/L with increased cardiac output shown by tachycardia and possibly a systolic murmur. Signs associated with particular forms of anaemia, e.g. jaundice in haemolytic or megaloblastic anaemia, koilonychia in iron deficiency, may be present and these are described with the individual anaemias.
Investigations
Anaemia is not, by itself, a sufficient diagnosis. Further assessment must be undertaken to establish the cause before treatment can be given (Box 8.1). This is done by clinical assessment (history, physical examination) and appropriate use of special investigations. A classification of anaemia according to whether red cells are large (macrocytic) or small (microcytic) is used to guide further investigations (Box 8.2) and further details on the specific types of anaemia are given in the appropriate chapters.
Usually associated with reduced red cell survival (haemolytic anaemias):
- Defects of haemoglobin, e.g. sickle cell, thalassaemia
- Defects of red cell metabolism, e.g. pyruvate kinase deficiency
- Defects of red cell membrane, e.g. hereditary spherocytosis
- Red cell aplasia/aplastic anaemia
Reduced red cell production due to:
- Haematinic deficiency (iron, B12, folate, B6)
- Marrow replacement, e.g. by tumour (leukaemia, myeloma, lymphoma)
- Marrow aplasia
Increased red cell destruction (haemolytic anaemia) due to:
- Immune destruction
- Red cell fragmentation syndromes
- Chemical and physical agents
- Infections
- Paroxysmal nocturnal haemoglobinuria
Systemic illnesses:
- Anaemia of chronic disease
- Renal failure, liver, cardiac, endocrine disease
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