Iron deficiency Anaemia

Related Subjects: |Iron deficiency Anaemia |Haemolytic anaemia |Macrocytic anaemia |Megaloblastic anaemia |Microcytic anaemia |Myelodysplasia |Myelofibrosis

⚠️ Iron deficiency anaemia in an older patient = gastrointestinal malignancy until proven otherwise. 👉 In men and postmenopausal women, always investigate with upper GI endoscopy and colonoscopy unless a clear non-GI cause is identified.

📖 About

• Iron deficiency anaemia (IDA) is the commonest cause of anaemia worldwide.
• In adults, IDA should be assumed to be due to blood loss until proven otherwise.
• Gastrointestinal malignancy must always be excluded 🚨

🧬 Aetiology

• Iron deficiency arises from inadequate intake, excess loss, or increased requirement.
• Most body iron is recycled from senescent red cells; depletion occurs gradually.
• A latent iron-depleted phase precedes the development of anaemia.

🩸 Causes

• Gastrointestinal blood loss (most common in adults)
• Menstrual blood loss
• Pregnancy (↑ iron requirements)
• Dietary deficiency
• Hookworm 🪱 (most common cause worldwide)
• Schistosomiasis
• Paterson–Brown–Kelly (Plummer–Vinson) syndrome

🩺 Clinical Features

• Fatigue, pallor, reduced exercise tolerance
• Exertional breathlessness
• Koilonychia – spoon-shaped nails
• Pallor of conjunctiva and palmar creases
• Brittle nails, hair loss, cheilosis, glossitis
• Flow murmurs (high-output state)
• Pica – craving ice (pagophagia) or clay (geophagia)

🔎 Investigations

• Microcytic, hypochromic anaemia (↓ MCV, ↓ MCH)
• Low reticulocyte count (reduced marrow response)
• Low serum ferritin (best single marker unless inflammation present)
• Plasma iron ↓, total iron-binding capacity (TIBC) ↑
• Transferrin saturation < 15% → impaired haemoglobin synthesis
• Soluble transferrin receptor ↑ (useful in inflammatory states)

📊 Key Components of Iron Studies

• Serum Iron: 10–30 µmol/L
• TIBC: 45–70 µmol/L
• Transferrin Saturation: 20–50%
• Ferritin: 15–300 µg/L (men), 15–200 µg/L (women)

🧾 Interpreting Iron Studies

Patterns of iron studies help distinguish iron deficiency from inflammatory and overload states.

🧪 Additional Investigations

• PR exam ± proctoscopy
• Upper GI endoscopy ± duodenal biopsy (coeliac disease)
• Colonoscopy (polyps, malignancy, colitis)
• Coeliac serology (anti-tTG, EMA)
• Urinalysis (haematuria)
• Capsule endoscopy / small bowel imaging for obscure bleeding

💊 Oral iron: Once-daily or alternate-day dosing is sufficient.
❌ Multiple daily dosing increases side effects without improving absorption.

💊 Management

• Identify and treat the underlying cause.
• Oral iron: Ferrous sulfate 200 mg once daily or alternate days for ≥3 months after Hb normalises.
• IV iron: Indicated if oral iron is not tolerated, malabsorbed, ineffective, or when rapid repletion is required.
• Blood transfusion: Reserved for severe or symptomatic anaemia or haemodynamic compromise.

🩸 Important: Transfusion treats the immediate oxygen-carrying deficit but does not correct iron deficiency. ➡️ Patients transfused for iron-deficiency anaemia should usually receive iron replacement (often IV) once stable to replenish iron stores and prevent relapse.

Teaching Commentary 🩸

Iron-deficiency anaemia reflects depleted iron stores and impaired erythropoiesis. Transfused red cells contain iron, but this iron is locked within donor haemoglobin and is not immediately available to the patient’s bone marrow. Without iron replacement, haemoglobin commonly falls again once transfused cells senesce. UK guidance therefore emphasises iron therapy as definitive treatment, with transfusion reserved for acute stabilisation. Unexplained IDA in men and postmenopausal women mandates urgent gastrointestinal investigation.

📚 References (UK)

• British Society for Haematology. Identification and management of preoperative anaemia in adults. Br J Haematol. 2024.
• British Society of Gastroenterology. Guidelines for the management of iron deficiency anaemia in adults. Gut. 2021.
• NICE. Blood transfusion (NG24). 2015 (updated).
• BMJ Best Practice. Iron deficiency anaemia in adults.