Define Iron Deficiency Anaemia. Describe its aetiology, pathophysiology, clinical features and investigations.

Definition

• Iron deficiency anaemia (IDA) is anaemia resulting from inadequate iron for haemoglobin synthesis.
• It is the commonest nutritional deficiency and the commonest cause of anaemia in children worldwide, and produces a microcytic, hypochromic anaemia.

Etiology

• Inadequate intake — prolonged exclusive milk feeding, delayed/inadequate complementary feeding, early introduction of cow's milk (low iron + occult GI blood loss).
• Increased demand — infancy, adolescence (growth spurt), prematurity/low birth weight (low iron stores).
• Blood loss — hookworm infestation (important in India), chronic GI bleeding, Meckel's diverticulum, menorrhagia in adolescents.
• Malabsorption — coeliac disease.

Pathophysiology (stages)

Depletion of iron stores (low ferritin) → Iron-deficient erythropoiesis (low serum iron, high TIBC) → Microcytic, hypochromic anaemia

Clinical Features

• Pallor, easy fatigue, poor appetite, irritability and lethargy.
• Pica (eating soil/ice), koilonychia (spoon-shaped nails), glossitis, angular stomatitis.
• Impaired cognition, learning and psychomotor development — an important, sometimes irreversible consequence in young children.
• Reduced exercise tolerance and increased susceptibility to infections.

Investigations

• Haemogram — low haemoglobin with low MCV, MCH, MCHC (microcytic hypochromic) and a raised RDW (anisocytosis).
• Peripheral smear — microcytic hypochromic red cells, pencil cells, target cells.
• Serum ferritin (low) — the best single indicator of iron stores (but rises with infection/inflammation).
• Low serum iron, high total iron-binding capacity (TIBC), low transferrin saturation; raised red-cell distribution width.

Management

• Oral iron — elemental iron 3–6 mg/kg/day; continue for 2–3 months after the haemoglobin normalises to replenish stores.
• A reticulocytosis in 5–7 days and a rising Hb in 2–4 weeks confirm a response.
• Dietary advice — iron-rich foods (green leafy vegetables, pulses, jaggery, meat), and vitamin-C-containing foods to aid absorption; limit excess cow's milk.
• Treat the cause — deworming for hookworm; investigate for blood loss if the response is poor.
• Parenteral iron or transfusion only for malabsorption, non-adherence or very severe/symptomatic anaemia.

Prevention

• Exclusive breastfeeding for 6 months, then timely iron-rich complementary feeding.
• Iron and folic acid supplementation (national Anaemia Mukt Bharat programme) for infants, children, adolescents and pregnant women.
• Periodic deworming; delayed cord clamping at birth; food fortification.

Epidemiology

• The commonest micronutrient deficiency globally; peak risk in infancy (6–24 months) and adolescence.
• Very common in India — targeted by national anaemia-control programmes.

Grading of Anaemia (WHO)

• Mild, moderate and severe categories by haemoglobin level (age-specific cut-offs).
• Severity guides urgency — severe symptomatic anaemia may need admission/transfusion.

Stages of Iron Depletion

• Iron depletion — falling ferritin, normal Hb.
• Iron-deficient erythropoiesis — low serum iron, high TIBC, normal Hb.
• Iron deficiency anaemia — the microcytic hypochromic anaemia.

Monitoring the Response to Iron

• Reticulocytosis by day 5–7; a rise in Hb of ~1 g/dL every 2–3 weeks.
• Failure to respond → check adherence, ongoing blood loss, wrong diagnosis (thalassaemia) or malabsorption.

Indications for Parenteral Iron / Transfusion

• Parenteral (IV) iron — malabsorption, intolerance of/non-adherence to oral iron, or chronic ongoing loss.
• Blood transfusion — only for very severe, symptomatic anaemia or heart failure (given slowly/in small aliquots).

Consequences of Untreated Ida

Beyond anaemia, chronic iron deficiency impairs cognitive development, learning and behaviour (some effects being irreversible), reduces immunity and work/school performance, and in pregnancy increases the risk of low birth weight and prematurity.