Adolescent Medicine · Supplementary · from Adolescent Medicine

Case 2: Eating Disorder — Bulimia Nervosa

Patient Presentation

Demographics: 17-year-old female high school junior, member of the dance team

Chief Complaint: "My mom made me come in. She found out I've been throwing up after meals."

History of Present Illness: The patient is brought to the adolescent medicine clinic by her mother, who discovered her daughter self-inducing vomiting after dinner three days ago. When confronted, the patient initially denied it but subsequently admitted to a pattern of binge eating followed by purging that began approximately 8 months ago. She describes episodes occurring 4-5 times per week, typically in the evening after school or after stressful events.

During binge episodes, she consumes large quantities of food — typically entire boxes of cereal, bags of chips, ice cream, and cookies — in a rapid, uncontrollable fashion, usually within a 1-2 hour period while home alone. She describes a sense of loss of control during these episodes and profound shame afterward. She induces vomiting by inserting her fingers into her throat, usually within 30 minutes of the binge. She also reports misusing over-the-counter laxatives (bisacodyl) 2-3 times per week to "get rid of" remaining food and intermittently restricting her intake on non-binge days to 800-1000 calories.

The behavior began after a dance team coach commented on her appearance, saying she "looked like she had gained weight over the summer" in front of her teammates. She reports preoccupation with body shape and weight, weighing herself 3-5 times daily, and feeling that her self-worth is primarily determined by her appearance. She has maintained a relatively stable weight, which she notes with frustration, as her goal is to lose "at least 10 more pounds."

She reports recent episodes of dizziness upon standing, intermittent heart palpitations, heartburn, sore throat, and swollen cheeks. She admits to fatigue and difficulty concentrating in school. She denies suicidal ideation but acknowledges feeling "worthless" and "disgusted with myself" at times.

Past Medical History:

• No chronic illnesses
• No prior psychiatric history or eating disorder diagnosis
• Menarche at age 13; regular periods until 3 months ago (now irregular)
• No hospitalizations or surgeries
• Wisdom teeth removed at age 16

Medications:

• Bisacodyl (OTC stimulant laxative) — 2-3 tablets, 2-3 times per week
• No prescription medications
• No supplements

Social History:

• 11th grade student; previously excellent student (GPA 3.8), grades declining this semester
• Member of the school dance team (practices 5 days/week, performances monthly)
• Lives with mother, stepfather, and 8-year-old half-sister
• Parents divorced when she was 10; describes this as a "difficult time"
• Denies tobacco, alcohol, or drug use
• Denies current sexual activity; had one previous sexual partner; used condoms
• Active social media use (Instagram, TikTok) — follows multiple "fitness" and "body transformation" accounts
• Reports 2-3 close friends but has been socially withdrawing over the past 3 months
• HEADSS assessment: positive for body image concerns, social withdrawal, and academic decline

Family History:

• Mother: history of depression, treated with SSRI
• Maternal aunt: anorexia nervosa in her 20s (hospitalized)
• Father: alcohol use disorder
• No family history of thyroid disease or metabolic disorders

Physical Examination

• Vital Signs: BP 98/62 mmHg (supine), 82/54 mmHg (standing — orthostatic), HR 58 bpm (supine), 82 bpm (standing — orthostatic), RR 16/min, Temp 36.2°C, Weight 56.8 kg, Height 168 cm, BMI 20.1 kg/m² (25th percentile for age)
• General: Alert, cooperative but guarded adolescent female; appears stated age; makes limited eye contact; Tanner stage V
• HEENT:
• Bilateral parotid gland enlargement (non-tender, firm)
• Dental erosion on the lingual surfaces of upper incisors and premolars (perimolysis); several carious teeth
• Pharyngeal erythema; soft palate petechiae
• Dry mucous membranes
• Subconjunctival hemorrhage in the left eye (likely from forceful vomiting)
• Cardiovascular: Bradycardic but regular rhythm; no murmurs; orthostatic changes as noted above
• Abdomen: Mild epigastric tenderness; no distension; bowel sounds present and hyperactive; no hepatosplenomegaly
• Extremities: Cool peripherally; calluses on the dorsal surface of the right index and middle finger metacarpophalangeal joints (Russell sign)
• Skin: Dry skin; mild lanugo-like hair on forearms; no bruising; no self-harm scars
• Neurological: Alert and oriented; mild difficulty with concentration; cranial nerves intact; DTRs 1+ globally (hyporeflexia)

Workup and Results

Laboratory Studies:

Imaging/Additional Studies:

• ECG: Sinus bradycardia at 58 bpm; prolonged QTc interval at 478 ms (normal <460 ms for females); flattened T-waves in leads V2-V4; presence of U-waves — changes consistent with hypokalemia
• DEXA scan (to be ordered): Recommended to assess bone mineral density given menstrual irregularity and nutritional compromise

Clinical Image

Educational diagram illustrating the multi-system medical complications of bulimia nervosa, including electrolyte disturbances, dental erosion, parotid enlargement, cardiac arrhythmias, esophageal injury, and metabolic alkalosis. Source: Educational illustration.

Diagnosis

Bulimia Nervosa, Purging Type — Moderate Severity (8-13 episodes per week) with Medical Complications

Key Diagnostic Criteria (DSM-5):

• Recurrent episodes of binge eating: consuming an objectively large amount of food in a discrete time period with a sense of loss of control (criterion A)
• Recurrent inappropriate compensatory behaviors: self-induced vomiting, laxative misuse, caloric restriction (criterion B)
• Binge eating and compensatory behaviors occur at least once per week for 3 months — this patient exceeds this threshold at 4-5 times per week for 8 months (criterion C)
• Self-evaluation is unduly influenced by body shape and weight (criterion D)
• Disturbance does not occur exclusively during episodes of anorexia nervosa (criterion E) — BMI is 20.1, within normal range
• Severity: moderate (4-7 compensatory behavior episodes per week; she reports 4-5 purging plus 2-3 laxative misuse episodes)

Medical Complications Present:

• Hypokalemic, hypochloremic metabolic alkalosis (from vomiting — loss of HCl)
• Prolonged QTc interval (478 ms) — arrhythmia risk
• Hypomagnesemia
• Orthostatic hypotension with tachycardia (dehydration)
• Parotid gland hypertrophy (sialadenosis)
• Dental erosion (perimolysis)
• Russell sign (knuckle calluses from self-induced vomiting)
• Amenorrhea (hypothalamic — 3 months)

Treatment Plan

1. Acute medical stabilization (hospitalization criteria met):

• Admit to the adolescent medicine unit given: hypokalemia (K 2.9), prolonged QTc (478 ms), orthostatic hypotension, and bradycardia
• Continuous cardiac monitoring until QTc normalizes
• IV potassium replacement: KCl 40 mEq IV over 4 hours, then reassess; target K >3.5 mEq/L
• Oral magnesium supplementation: magnesium oxide 400 mg twice daily
• IV fluid resuscitation: normal saline 1 L over 4 hours, then reassess
• Monitor electrolytes every 6-8 hours during repletion
• Strict intake and output; supervised meals to prevent purging (1:1 observation for 1 hour after meals)
• Repeat ECG after potassium normalization

1. Nutritional rehabilitation:

• Registered dietitian consultation: establish regular meal pattern (3 meals, 2-3 snacks daily)
• Discontinue laxative misuse with gradual taper (not abrupt cessation, to prevent rebound constipation)
• Begin with 1500-1800 kcal/day and advance; refeeding syndrome risk is lower in BN than AN but should be monitored (electrolytes, especially phosphorus)

1. Psychotherapy (cornerstone of treatment):

• Cognitive-behavioral therapy for bulimia nervosa (CBT-BN): first-line evidence-based treatment; typically 20 sessions over 5 months
• Address body image distortions, cognitive distortions about weight and self-worth, and develop alternative coping strategies for emotional regulation
• Family-based treatment (FBT) component: engage mother in meal support and monitoring

1. Pharmacotherapy:

• Fluoxetine 20 mg daily, titrate to 60 mg (FDA-approved for BN in adults; commonly used in adolescents off-label); target dose of 60 mg is higher than the typical antidepressant dose
• Rationale: reduces binge-purge frequency by 50-70% in conjunction with CBT
• Monitor for SSRI side effects and suicidality (black box warning in adolescents)

1. Dental referral: Comprehensive dental evaluation and treatment plan for erosion and caries; advise against brushing immediately after vomiting (worsens erosion); use sodium bicarbonate rinse instead
2. Follow-up:

• Weekly weight monitoring (in gown, facing away from scale — to reduce weight fixation)
• Electrolytes weekly until stable, then monthly
• ECG repeat after electrolyte normalization
• DEXA scan at 6 months if amenorrhea persists
• Menstrual function monitoring — expect return with nutritional improvement

Key Learning Points

• Bulimia nervosa patients are often of normal weight, making the diagnosis less visually apparent than anorexia nervosa; a high index of suspicion is needed, especially in adolescents involved in appearance-focused activities (dance, gymnastics, figure skating, wrestling).
• The characteristic electrolyte pattern in purging-type bulimia is hypokalemic, hypochloremic metabolic alkalosis due to loss of gastric acid (HCl); in contrast, laxative misuse causes a non-anion-gap metabolic acidosis with hypokalemia.
• A prolonged QTc interval (>460 ms in females, >450 ms in males) is a medical emergency in eating disorders because it predisposes to torsades de pointes and sudden cardiac death; potassium and magnesium must be repleted urgently.
• CBT specifically adapted for bulimia nervosa (CBT-BN) is the most effective treatment, with 40-60% of patients achieving full remission; fluoxetine at 60 mg/day is the only FDA-approved medication and works synergistically with psychotherapy.
• Russell sign (calluses on the dorsal knuckles from contact with teeth during self-induced vomiting), parotid enlargement, and dental perimolysis are classic physical examination findings that should prompt confidential inquiry about eating disorder behaviors in adolescents.

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