A 2-year-old child is brought with weight 60% of expected for age, bilateral pitting pedal oedema, skin changes (flaky-paint dermatosis), and fine reddish discoloration of hair. The diagnosis is Kwashiorkor. The primary biochemical mechanism responsible for oedema in this condition is:

• A Hyponatraemia causing osmotic shift of fluid
• B Elevated ADH secretion causing water retention
• C Hypoalbuminaemia reducing oncotic pressure leading to transudation ✓
• D Iron deficiency anaemia reducing colloid osmotic pressure

Explanation

Kwashiorkor is primarily caused by severe protein deficiency (with relatively adequate caloric intake). The central mechanism of oedema is hypoalbuminaemia: serum albumin falls below 2.8 g/dL, reducing plasma oncotic (colloid osmotic) pressure. This allows fluid to shift into the interstitial compartment. Flaky-paint dermatosis, oedema, and discoloured (flag sign) hair are hallmarks. Iron deficiency anaemia reduces O2 carrying capacity but does not cause oedema. ADH elevation is secondary, not primary.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.