ABC of Clinical Haematology

Drew Provan, Drew Provan

• Éditeur: BMJ Books
• Année: 2018
• ISBN:
  9781118892480
• Édition: 4
• Sujet: Medicina
• Sous-sujet: Ematologia

Thoroughly revised and updated, ABC of Clinical Haematology is an essential guide and introduction to clinical haematology and to the treatment and management of common blood related disorders.

The fourth edition contains new chapters that reflect the most recent developments whilst other chapters have been extensively revised to include the new tests and treatments that are now available for certain conditions such as chronic leukaemia, multiple myeloma and bleeding disorders.

With contributions from leading experts in their respective fields, this text provides an ideal reference for primary care practitioners and other healthcare professionals working with patients who have blood related problems.

CHAPTER 1
Iron‐Deficiency Anaemia

Drew Provan¹ and Catherine Booth²

¹ Department of Haematology, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK

² Barts and the London NHS Trust, London, UK

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OVERVIEW

• Iron deficiency is the commonest cause of anaemia worldwide and is frequently seen in general practice.
• The anaemia of iron deficiency is caused by defective synthesis of haemoglobin, resulting in red cells that are smaller than normal (microcytic) and contain reduced amounts of haemoglobin (hypochromic).

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Iron metabolism

Iron has a pivotal role in many metabolic processes, and the average adult contains 3–5 g of iron, of which two‐thirds is in the oxygen‐carrying molecule haemoglobin.

A normal Western diet provides about 15 mg of iron daily, of which 5–10% is absorbed (~1 mg), principally in the duodenum and upper jejunum, where the acidic conditions help the absorption of iron in the ferrous form. Absorption is helped by the presence of other reducing substances, such as hydrochloric acid and ascorbic acid. The body has the capacity to increase its iron absorption in the face of increased demand – for example, in pregnancy, lactation, growth spurts and iron deficiency (Box 1.1).

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Box 1.1 Risk factors for development of iron deficiency.

• Age: infants (especially if history of prematurity); adolescents; premenopausal women; old age
• Gender: increased risk in women
• Reproduction: pregnancy, breast feeding
• Travel/country of origin: parasites (e.g. hookworm, schistosoma)
• Gastrointestinal pathology: appetite or weight changes; changes in bowel habit; bleeding from rectum/melaena; gastric or bowel surgery
• Drug history: especially aspirin and non‐steroidal anti‐inflammatories
• Social history: diet, especially vegetarianism, age of weaning of infants

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Once absorbed from the bowel, iron is transported across the mucosal cell to the blood, where it is carried by the protein transferrin to developing red cells in the bone marrow. Iron stores comprise ferritin, a labile and readily accessible source of iron, and haemosiderin, an insoluble form found predominantly in macrophages.

About 1 mg of iron a day is lost from the body in urine, faeces, sweat and cells shed from the skin and gastrointestinal tract. Menstrual losses of an additional 20 mg a month, and the increased requirements of pregnancy (500–1000 mg) contribute to the higher incidence of iron deficiency in women of reproductive age (Table 1.1, Box 1.2).

Table 1.1 Daily dietary iron requirements.

Male	1 mg
Adolescence	2–3 mg
Female (reproductive age)	2–3 mg
Pregnancy	3–4 mg
Infancy	1 mg
Maximum bioavailability from normal diet	~4 mg

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Box 1.2 Causes of iron‐deficiency anaemia.

Most iron‐deficiency anaemia is the result of blood loss, especially in affluent countries.

Reproductive system

• Menorrhagia

Gastrointestinal tract

Bleeding

• Oesophagitis
• Oesophageal varices
• Hiatus hernia (ulcerated)
• Peptic ulcer
• Inflammatory bowel disease
• Haemorrhoids (rarely)
• Carcinoma: stomach, colorectal
• Angiodysplasia
• Hereditary haemorrhagic telangiectasia (rare)
• Hookworm infection – commonest cause of iron deficiency worldwide

Malabsorption

• Coeliac disease
• Atrophic gastritis (also may result from iron de...