Discuss the causes, clinical features, investigations and management of iron deficiency anaemia.

Introduction

Iron deficiency is the commonest nutritional deficiency and the commonest cause of anaemia worldwide, and is of enormous public health significance in India, where the National Family Health Survey has repeatedly shown very high prevalence among women and children.

Iron Physiology

Total body iron is 3–4 g, of which two-thirds is in haemoglobin. Daily requirement is about 1 mg in adult men and 2 mg in menstruating women, rising sharply in pregnancy. Absorption occurs in the duodenum and upper jejunum, is enhanced by ascorbic acid, gastric acid and haem iron (from meat), and inhibited by phytates (cereals), tannins (tea and coffee), calcium, antacids and proton pump inhibitors. Hepcidin, raised in inflammation, blocks iron release from enterocytes and macrophages — the mechanism underlying anaemia of chronic disease.

Causes

Clinical Features

• General anaemia symptoms: fatigue, exertional dyspnoea, palpitations, headache, dizziness, poor concentration and reduced work capacity; angina or heart failure in the elderly.
• Signs specific to iron deficiency:
• Koilonychia — spoon-shaped, brittle nails
• Angular stomatitis and atrophic glossitis with a smooth, sore tongue
• Dysphagia from a post-cricoid web — the Plummer–Vinson (Paterson–Brown–Kelly) syndrome of iron deficiency, dysphagia and oesophageal web, which carries a risk of post-cricoid carcinoma
• Pica — craving for non-food substances, classically pagophagia (ice), mud or clay; particularly common in children in India
• Dry skin, brittle hair with diffuse hair loss, blue sclerae
• Restless legs syndrome — a frequently overlooked association
• Impaired cognitive development in children and reduced work productivity in adults — the reason this is a public health priority, not merely a haematological problem.

Investigations

• Peripheral smear: microcytic hypochromic red cells with anisocytosis and poikilocytosis, pencil cells and target cells; thrombocytosis is common.
• Mentzer index (MCV ÷ RBC count): > 13 suggests iron deficiency; < 13 suggests thalassaemia trait — a useful bedside screening tool where HPLC is not readily available.
• Investigate the CAUSE — the essential second half of the workup: stool for occult blood and ova/parasites, upper GI endoscopy and colonoscopy in men and postmenopausal women (and in younger patients with symptoms or no obvious source), coeliac serology, urinalysis, and gynaecological assessment for menorrhagia.

Management

1. Treat the underlying cause — this is what prevents recurrence: manage menorrhagia, treat peptic ulcer and *H. pylori*, resect malignancy, deworm with albendazole, treat coeliac disease, and review NSAID use.

2. Oral iron — first-line

• Ferrous salts (sulphate, fumarate, gluconate) are cheap and effective.
• Take on an empty stomach with vitamin C (or citrus juice) to maximise absorption; avoid tea, coffee, milk, calcium and antacids within 2 hours — an issue of real practical importance in India, where tea is taken with meals.
• Alternate-day dosing is increasingly favoured over multiple daily doses: it produces better fractional absorption (by avoiding hepcidin induction) and fewer side effects, with equivalent haemoglobin response.
• Adverse effects — nausea, epigastric discomfort, constipation, metallic taste and black stools (harmless, but must be explained or it will be mistaken for melaena). Side effects are the main cause of non-adherence.
• Expected response — reticulocytosis peaks at 5–10 days, haemoglobin rises by about 2 g/dL every 3 weeks, and treatment is continued for a further 3 months after the haemoglobin normalises to replenish stores. Failure of the haemoglobin to rise should prompt review of adherence, absorption, continuing blood loss, or an incorrect diagnosis.

3. Parenteral iron — for intolerance of oral iron, malabsorption, continuing losses exceeding oral replacement, chronic kidney disease on erythropoietin, inflammatory bowel disease, and late pregnancy where rapid correction is needed. Modern preparations (iron sucrose, ferric carboxymaltose) are well tolerated; observe for anaphylaxis.

4. Blood transfusion — reserved for haemodynamic instability, active major bleeding, or severe symptomatic anaemia (especially with cardiac decompensation). Transfuse cautiously and slowly in chronic severe anaemia to avoid precipitating pulmonary oedema; consider concurrent diuretic.

5. Prevention — dietary counselling (green leafy vegetables, jaggery, pulses, meat, and vitamin C sources with meals), iron and folic acid supplementation programmes for pregnant women, adolescents and children, food fortification, deworming programmes, and delayed cord clamping at birth.