A 19-year-old woman with anorexia nervosa (restricting type, BMI 14.5) is admitted. On day 3 of refeeding, she develops oedema, muscle weakness, cardiac arrhythmias, and confusion. Serum phosphate is 0.4 mmol/L. What is this syndrome and what is the pathophysiological trigger?

• A Wernicke's encephalopathy; thiamine deficiency from inadequate supplementation
• B Hyponatraemic encephalopathy; inappropriate ADH release due to weight gain
• C Superior mesenteric artery syndrome; compression of duodenum by refeeding-induced fat deposition
• D Refeeding syndrome; insulin-driven intracellular shift of phosphate, potassium, and magnesium, causing hypophosphataemia, hypokalaemia, and hypomagnesaemia ✓

Explanation

Refeeding syndrome occurs when severely malnourished patients receive rapid carbohydrate repletion. Carbohydrate stimulates insulin secretion, which drives glucose, phosphate, potassium, and magnesium into cells (anabolism). The patient's total body stores of these electrolytes are already severely depleted (masked by normal serum levels pre-refeeding). The resulting hypophosphataemia (<0.5 mmol/L) impairs ATP and 2,3-DPG synthesis, causing cardiac arrhythmias, respiratory failure, rhabdomyolysis, and neurological dysfunction. Prevention requires slow caloric increase (10–20 kcal/kg/day initially), electrolyte supplementation before and during refeeding, and thiamine administration.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.