Eating disorders: recognition and medical instability — formative SAQs

SAQ 1 — Fainting 15-year-old runner (10 marks)

A 15-year-old cross-country runner is brought to the emergency department after fainting at school. Over three months she has cut out all carbohydrates, runs before dawn, and her periods have stopped. Her weight sits in the "healthy" band. Her resting heart rate is 38 beats per minute and rises markedly when she stands up. She believes she is "a bit overweight." [3] [4]

Questions

1. Outline your immediate recognition, screening and instability assessment. (4 marks) [3]
2. List the physiological red flags that would mandate admission and state which are present here. (4 marks) [4]
3. Give your disposition and immediate management priorities, and the key pitfall in this presentation. (2 marks) [5]

Model answer

Recognition, screening and instability (4). Recognise an eating disorder with atypical-anorexia features: restriction, driven exercise, amenorrhoea, syncope and body-image disturbance despite a non-low weight. See her alone, apply SCOFF (two or more positive supports the diagnosis) and a HEEADSSS psychosocial frame. Quantify instability: weigh in a gown and plot percentage of median body mass index; measure lying and standing heart rate and blood pressure (a standing test), temperature, and a 12-lead ECG for QTc and rhythm; check bedside glucose and electrolytes. [3] [4]

Red flags and those present (4). Red flags (Junior MARSIPAN framing): severe resting bradycardia (under about 40 beats per minute), hypotension (under about 80/50), a marked postural heart-rate rise or systolic blood-pressure drop, a prolonged QTc, hypothermia, syncope, hypoglycaemia and rapid weight loss. Present here: severe bradycardia (38), a marked postural heart-rate rise, and syncope — each alone would mandate admission. [4] [6]

Disposition, priorities and pitfall (2). Same-day medical admission with cardiac monitoring; correct potassium, magnesium and phosphate and treat hypoglycaemia; begin cautious refeeding because feeding triggers refeeding syndrome. The key pitfall is reassurance on the basis of a "healthy" weight — atypical anorexia carries the same danger as anorexia nervosa. [5] [3]

SAQ 2 — Normal-weight adolescent with vomiting and palpitations (10 marks)

A 16-year-old presents with palpitations, muscle weakness and a first faint. Her weight is normal. Her mother reports she disappears to the bathroom after meals. On examination there is callus on the back of one hand and enlarged parotid glands. [6] [3]

Questions

1. What is the most likely diagnosis and which physiological mechanism explains her symptoms? (3 marks) [6]
2. Outline your focused assessment and investigations. (4 marks) [3]
3. Give your immediate management and disposition, including suicide-risk assessment. (3 marks) [3]

Model answer

Diagnosis and mechanism (3). Bulimia nervosa: recurrent binges with inappropriate compensation (self-induced vomiting), supported by Russell's sign (callus on the dorsum of the hand from inducing vomiting) and parotid enlargement. Her palpitations and weakness reflect hypokalaemia (with hypomagnesaemia and metabolic alkalosis) from purging, which prolongs cardiac repolarisation and predisposes to arrhythmia — explaining the faint. [6] [3]

Assessment and investigations (4). History alone with HEEADSSS: binge frequency, purging methods, laxative and diuretic use, exercise, mood and self-harm; apply SCOFF. Examination for bradycardia or hypotension, dental erosion, parotid enlargement, Russell's sign. Investigations: 12-lead ECG for QTc and arrhythmia; bloods for full blood count, urea and electrolytes (expect low potassium), magnesium, phosphate, calcium, glucose, and venous blood gas if acutely unwell; targeted tests to exclude mimics where the picture is atypical. [3] [6]

Management, disposition and suicide risk (3). Correct potassium and magnesium per local protocol with cardiac monitoring; admit if the QTc is prolonged, arrhythmia is present, or potassium is dangerously low. Arrange multidisciplinary care with specialist eating-disorder mental-health therapy (cognitive-behavioural therapy adapted for eating disorders is first-line for bulimia). Screen explicitly for suicidality — death in eating disorders is as much from suicide as from medical causes — and use a crisis pathway if risk is high. [2] [3]