What are the differences in diagnosis and treatment of bulimia nervosa versus anorexia nervosa binge-purge type in pediatric patients?

Diagnostic Distinction Between Bulimia Nervosa and Anorexia Nervosa Binge-Purge Type in Pediatric Patients

The critical diagnostic difference is body weight: anorexia nervosa binge-purge type requires significantly low body weight (typically <85% ideal body weight or BMI <5th percentile for age in children), while bulimia nervosa patients maintain normal or above-normal weight despite engaging in similar binge-eating and purging behaviors. 1

Key Diagnostic Criteria

Anorexia Nervosa Binge-Purge Type

• Weight status: Significantly underweight with BMI percentile below expected for age and height 1, 2
• Behavioral pattern: Restrictive eating combined with episodes of binge eating followed by compensatory purging behaviors (vomiting, laxatives, excessive exercise) 3
• Psychological features: Intense fear of weight gain, distorted body image, and preoccupation with food and weight despite being underweight 1
• Medical complications: Primarily related to malnutrition and underweight status, including bradycardia, hypothermia, orthostatic changes, and electrolyte abnormalities 4, 3

Bulimia Nervosa

• Weight status: Normal weight, overweight, or fluctuating weight—this is the defining distinction 5, 6
• Behavioral pattern: Recurrent episodes of binge eating followed by compensatory behaviors (purging), but without the severe caloric restriction that leads to significant weight loss 5, 6
• Psychological features: Similar preoccupation with body shape and weight, but without the extreme underweight status 6
• Medical complications: Primarily related to purging behaviors, including hydroelectrolyte disturbances, acid-base abnormalities, dental erosion, and esophageal complications 3

Clinical Assessment Priorities

Initial Evaluation for Both Conditions

• Vital signs assessment: Measure temperature, resting heart rate, blood pressure, and orthostatic changes immediately 1, 4
• Anthropometric measurements: Document height, weight, BMI percentile for age, and compare to previous growth charts to identify weight trajectory 1, 4
• Physical examination: Look for signs of malnutrition (muscle wasting, lanugo) in suspected anorexia nervosa versus signs of purging (dental erosion, Russell's sign on knuckles) more prominent in bulimia nervosa 1, 4

Laboratory and Cardiac Workup

• ECG: Obtain immediately for both conditions, especially critical in restrictive eating disorders and severe purging behaviors to assess for QTc prolongation 1, 4
• Complete blood count: Assess for anemia and leukopenia from malnutrition 1, 4
• Comprehensive metabolic panel: Check electrolytes (particularly potassium), liver enzymes, and renal function to identify complications from purging or malnutrition 1, 4

Critical pitfall: More than half of adolescents with eating disorders have normal laboratory results despite being medically unstable—never assume normal labs exclude serious illness 4, 7

Treatment Differences

Anorexia Nervosa Binge-Purge Type in Pediatrics

• First-line treatment: Family-based therapy where parents take full control of eating decisions and meal planning for weight restoration 1, 2, 5
• Primary goal: Nutritional rehabilitation and weight restoration with individualized weekly weight gain targets 1, 2
• Medication role: No FDA-approved medications for pediatric anorexia nervosa; pharmacotherapy is not recommended as primary treatment 1, 5
• Hospitalization threshold: More aggressive criteria apply—consider admission at higher weight percentiles than adults, particularly with heart rate <50 bpm daytime or <45 bpm nighttime, temperature <36°C, or orthostatic instability 7

Bulimia Nervosa in Pediatrics

• First-line treatment: Family-based therapy for adolescents with involved caregivers, nearly equally effective as cognitive-behavioral therapy 1, 5
• Primary goal: Normalize eating patterns, eliminate binge-purge cycles, and address psychological aspects without necessarily requiring weight restoration 1
• Medication consideration: While fluoxetine 60mg daily is recommended for adults with bulimia nervosa (either initially or if minimal response to psychotherapy by 6 weeks), no medications are FDA-approved for pediatric bulimia nervosa 1, 5
• Hospitalization threshold: Generally less urgent than anorexia nervosa unless severe purging causes dangerous electrolyte abnormalities or cardiac complications 7, 3

Prognostic Considerations

Mortality risk: Both conditions carry significant mortality risk, with cardiac complications responsible for at least one-third of deaths in eating disorders 2. However, anorexia nervosa typically has higher mortality rates due to complications of severe malnutrition 6.

Treatment urgency: Children and adolescents with anorexia nervosa have the best prognosis when treated rapidly and aggressively, as early intervention is associated with improved outcomes 2, 7. The same principle applies to bulimia nervosa, though the medical urgency is typically lower unless severe purging behaviors are present 5.