WHAT IS ANEMIA?
- 1WHAT IS THE MEANING OF ANEMIA?
- Anaemia is a group of diseases characterised by a decrease in either haemoglobin (Hb) or the volume of red blood cells (RBCs), resulting in the decreased oxygen-carrying capacity of the blood. The World Health Organization defines anemia as Hb less than 13 g/dL (<130 g/L; <8.07 mmol/L) in men or less than 12 g/dL (<120 g/L; <7.45 mmol/L) in women.
- 2WHAT ARE THE CAUSES OF ANEMIAS?
- The functional classification of anaemias is found in Fig. 1–1. The most common anaemias are included in this chapter.
FIGURE 1–1. Functional classification of anaemia. Each of the major categories of anaemia (hyperproliferative, maturation disorders, and haemorrhage/hemolysis) can be further subclassified according to the functional defect in the several components of normal erythropoiesis.
- Morphologic classifications are based on cell size. Macrocytic cells are larger than normal and are associated with deficiencies of vitamin B12 or folic acid. Microcytic cells are smaller than normal and are associated with iron deficiency, whereas normocytic anaemia may be associated with recent blood loss or chronic disease.
- Iron-deficiency anaemia (IDA) can be caused by inadequate dietary intake, inadequate gastrointestinal (GI) absorption, increased iron demand (e.g., pregnancy), blood loss, and chronic diseases.
- Vitamin B12– and folic acid–deficiency anaemias can be caused by inadequate dietary intake, decreased absorption, and inadequate utilisation. Deficiency of intrinsic factor causes decreased absorption of vitamin B12 (i.e., pernicious anaemia). Folic acid–deficiency anaemia can be caused by hyper-utilisation due to pregnancy, hemolytic anaemia, myelofibrosis, malignancy, chronic inflammatory disorders, long-term dialysis, or growth spurt. Drugs can cause anaemia by reducing the absorption of folate (e.g., phenytoin) or through folate antagonism (e.g., methotrexate).
- Anaemia of inflammation (AI) is a newer term used to describe both anaemias of chronic disease and anaemia of critical illness. AI is anaemia that traditionally has been associated with infectious or inflammatory processes, tissue injury, and conditions associated with the release of proinflammatory cytokines. See Table 1–1 for diseases associated with AI. For information on anaemia of chronic kidney disease.
- Age-related reductions in bone marrow reserve can render elderly patients more susceptible to anaemia caused by multiple minor and often unrecognised diseases (e.g., nutritional deficiencies) that negatively affect erythropoiesis.
- Pediatric anaemias are often due to a primary hematologic abnormality. The risk of IDA is increased by rapid growth spurts and dietary deficiency.
- 3WHAT ARE THE SIGNS AND SYMPTOMS OF ANEMIAS?
- Signs and symptoms depend on the rate of development and age and cardiovascular status of the patient. Acute-onset anaemia is characterised by cardiorespiratory symptoms such as palpitations, angina, orthostatic lightheadedness, and breathlessness. Chronic anaemia is characterised by weakness, fatigue, headache, orthopnea, dyspnea on exertion, vertigo, faintness, cold sensitivity, pallor, and loss of skin tone.
- IDA is characterised by glossal pain, smooth tongue, reduced salivary flow, pica (compulsive eating of nonfood items), and pagophagia (compulsive eating of ice).
- Neurologic effects (e.g., numbness and ataxia) of vitamin B12 deficiency may occur in the absence of hematologic changes. Psychiatric findings, including irritability, depression, and memory impairment, may also occur with vitamin B12 deficiency. Anaemia with folate deficiency is not associated with neurologic symptoms.