Clinical Vignette
Patient: "Ms. H," 25-year-old marketing executive, self-referred after her dentist noticed enamel erosion on the palatal surfaces of her teeth and asked if she had been vomiting.
Chief Concern: "I've been binging and purging for 7 years. I eat 3,000-5,000 calories in one sitting, then make myself throw up. I do this 5-6 times a week. My teeth are damaged. My throat is constantly sore. I hate myself for it but I can't stop."
History of Present Illness: Ms. H reports a 7-year pattern of recurrent binge eating followed by self-induced vomiting. Her typical binge episode involves consuming 3,000-5,000 calories in under 2 hours (an entire pizza, a pint of ice cream, a box of cookies, bread, and cheese). She describes binges as feeling 'out of control' — she cannot stop eating until the food is gone or she feels physically painful. Immediately after bingeing, she self-induces vomiting (5-6 times per week). She also uses laxatives 2-3 times weekly and exercises intensely on days she does not purge. Her weight is within the normal range (BMI 22.5) and has been stable for years. She restricts calories severely on non-binge days (500-800 calories). She describes her self-worth as 'entirely based on my weight and how I look.' She weighs herself 3-4 times daily. Russell's sign is present (calluses on knuckles from self-induced vomiting). Dental erosion on palatal surfaces. Parotid gland enlargement (bilateral 'chipmunk cheeks').
Medical History: Dental enamel erosion. Recurrent esophagitis. Hypokalemia (K+ 3.1 on recent lab). Parotid hypertrophy. Russell's sign.
Mental Status Exam: Well-groomed, normal weight. Parotid enlargement visible. Calluses on right knuckles. Speech normal. Mood 'disgusted with myself.' Affect ashamed, tearful. Thought process logical. Content: preoccupied with body shape, weight, and eating behavior. Self-worth equated with appearance. No psychotic symptoms. No suicidal ideation. Insight good: recognizes the behavior is harmful.
Step 1: Bulimia Nervosa DSM-5-TR Criteria
Criterion A: Recurrent episodes of binge eating characterized by: (1) eating a definitely large amount of food in a discrete period, (2) sense of lack of control during the episode.
(1) 3,000-5,000 calories in under 2 hours (objectively large). (2) Describes episodes as 'out of control' — cannot stop until food is gone or physical pain. MET.
Criterion B: Recurrent inappropriate compensatory behaviors to prevent weight gain: self-induced vomiting, misuse of laxatives, diuretics, fasting, or excessive exercise.
Self-induced vomiting (5-6x/week). Laxative misuse (2-3x/week). Excessive exercise. Severe caloric restriction on non-binge days. MET — multiple compensatory behaviors.
Criterion C: Binge eating and compensatory behaviors both occur at least once a week for 3 months.
5-6 binge-purge episodes weekly for 7 years. MET — far exceeds threshold.
Criterion D: Self-evaluation is unduly influenced by body shape and weight.
'Self-worth entirely based on weight and how I look.' Weighs herself 3-4 times daily. MET.
Criterion E: Does not occur exclusively during episodes of Anorexia Nervosa.
BMI 22.5 (normal weight). Does not meet AN Criterion A (significantly low weight). MET — normal weight, not AN.
Step 2: Distinguishing BN from AN Binge-Purge and BED
| Feature | Bulimia Nervosa | AN Binge-Purge Subtype | Binge Eating Disorder | This Patient |
|---|---|---|---|---|
| Weight | Normal or overweight | Significantly low body weight | Often overweight/obese | BN: BMI 22.5 (normal) |
| Binge eating | Present | Present | Present | Present |
| Compensatory behavior | Present (defining feature) | Present | ABSENT (defining absence) | Present: vomiting, laxatives, exercise |
| Body image distortion | Self-worth tied to weight | Perception of being overweight at low weight | Less prominent | BN: self-worth 'entirely' weight-based |
| Severity (DSM-5-TR) | Based on compensatory behavior frequency | Based on BMI | Based on binge frequency | Severe: 5-6x/week |
Severity Assessment
DSM-5-TR BN severity: Mild (1-3 episodes/week), Moderate (4-7), Severe (8-13), Extreme (≥14). Ms. H's 5-6 episodes/week places her at moderate severity. However, the co-occurrence of multiple compensatory methods (vomiting + laxatives + exercise + fasting) and medical complications (hypokalemia, dental erosion, esophagitis) elevates clinical concern.
Diagnostic Formulation
Diagnostic Conclusion
Bulimia Nervosa, Moderate (F50.2): All 5 DSM-5-TR criteria met. Seven-year binge-purge pattern at normal weight. Multiple compensatory behaviors. Self-worth tied to body shape/weight. Medical complications: hypokalemia (cardiac risk), dental erosion, esophagitis, parotid hypertrophy. Treatment: CBT-E (enhanced CBT for eating disorders — first-line, strongest evidence), SSRI augmentation (fluoxetine 60mg — the only FDA-approved medication for BN), medical monitoring of potassium and cardiac status.
Teaching Points
- Body weight is the primary distinguishing feature between BN and AN binge-purge subtype. If the patient is at a significantly low weight AND binge-purges, the diagnosis is AN binge-purge subtype. If the patient is at normal or elevated weight, the diagnosis is BN. AN 'trumps' BN diagnostically when low weight is present.
- Hypokalemia from purging is the most dangerous medical complication of BN. Potassium below 3.0 mEq/L carries risk of cardiac arrhythmia and sudden death. ECG and potassium monitoring are standard of care. Ms. H's K+ of 3.1 is in the danger zone.
- CBT-Enhanced (CBT-E) developed by Fairburn is the gold-standard treatment for BN. It addresses the maintenance cycle: dietary restriction → hunger → binge → purge → guilt → restriction. Breaking the restriction-binge cycle is central to treatment.
- Fluoxetine 60mg is the only FDA-approved medication for BN and is effective as monotherapy or augmentation to CBT. The effective dose for BN (60mg) is higher than the typical antidepressant dose (20mg).
- The dental signs of BN (enamel erosion on palatal surfaces of upper teeth from repeated exposure to gastric acid) and Russell's sign (calluses on knuckles from using fingers to induce vomiting) are clinical clues that dentists and primary care providers should recognize. These signs may be the first clinical evidence of an otherwise hidden disorder.