Clinical Vignette
Patient: "Ms. D," 17-year-old high school junior, brought by parents after school nurse noted BMI of 15.2 kg/m² and reported her fainting during PE class.
Chief Concern: Ms. D: "I'm not that thin. There are girls thinner than me. I eat enough — my parents are overreacting." Parents: "She's lost 40 pounds in 6 months. She exercises 3 hours a day. She counts every calorie. She wears baggy clothes to hide how thin she's gotten."
History of Present Illness: Ms. D was at a healthy weight (BMI 22) until 6 months ago when she began restricting caloric intake after a comment from a gymnastics coach about 'competition weight.' She progressively reduced her intake from approximately 2000 calories/day to her current 400-600 calories/day, consisting primarily of plain vegetables and diet drinks. She has lost 40 pounds (from 135 to 95 lbs at a height of 5'6"). She exercises compulsively: 90-minute morning run, 60-minute evening workout, and walks between classes. She refuses to eat meals with her family, prepares elaborate meals for others but does not eat them herself, and cuts food into tiny pieces on the rare occasions she eats at the table. She denies being underweight despite objective BMI of 15.2 (severely underweight). She body-checks in the mirror multiple times daily, perceiving herself as 'normal' or 'still too big.' Medical complications: fainting (vasovagal), cold intolerance, lanugo (fine body hair), amenorrhea (loss of menstruation for 4 months), bradycardia (HR 48), and orthostatic hypotension.
Medical History: Bradycardia (HR 48). Orthostatic hypotension. Amenorrhea (4 months). Lanugo. Labs: low albumin, low phosphorus, prolonged QTc on ECG.
Mental Status Exam: Cachectic appearance. Wearing oversized sweatshirt. Alert. Speech normal. Mood 'fine.' Affect flat. Denies distress about weight. When informed her BMI is severely low, states: 'I still need to lose a few more pounds.' No psychotic symptoms. Insight severely impaired regarding body weight/size. Denies any physical symptoms despite documented medical abnormalities.
Step 1: Anorexia Nervosa DSM-5-TR Criteria
Criterion A: Restriction of energy intake relative to requirements, leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health.
Caloric intake 400-600 kcal/day (requirement: ~2000). BMI 15.2 kg/m² (significantly low for age/sex). 40 lbs weight loss in 6 months. MET — SEVERELY LOW WEIGHT.
Criterion B: Intense fear of gaining weight or of becoming fat, or persistent behavior that interferes with weight gain.
Restricts calories to 400-600/day. Exercises compulsively (3 hours daily). Refuses family meals. States she 'still needs to lose a few more pounds' at BMI 15.2. MET.
Criterion C: Disturbance in the way in which one's body weight or shape is experienced, undue influence of body weight on self-evaluation, or persistent lack of recognition of the seriousness of the current low body weight.
Denies being underweight at BMI 15.2. Perceives herself as 'normal' or 'too big.' Denies medical seriousness despite bradycardia, amenorrhea, and fainting. All three C criteria features present. MET — all three features.
Step 2: Subtype and Severity
DSM-5-TR subtype and severity classification:
Restricting Type
No binge eating or purging (vomiting, laxatives, diuretics) in the past 3 months. Weight loss achieved exclusively through caloric restriction and excessive exercise. RESTRICTING TYPE.
Severity: Extreme (BMI < 15)
BMI 15.2 approaches the 'extreme' threshold. DSM-5-TR severity: Mild (BMI ≥17), Moderate (16-16.99), Severe (15-15.99), Extreme (<15). Current: SEVERE. SEVERITY: SEVERE.
Medical Risk Assessment
Ms. D is at HIGH medical risk: bradycardia (HR 48), prolonged QTc (risk of fatal arrhythmia), orthostatic hypotension, amenorrhea, low phosphorus (refeeding syndrome risk), and lanugo. Medical stabilization is the IMMEDIATE priority before psychological treatment of the eating disorder.
Diagnostic Formulation
Diagnostic Conclusion
Anorexia Nervosa, Restricting Type, Severe (F50.01): All 3 DSM-5-TR criteria met. Restricting subtype (no binge/purge). Severity: severe (BMI 15.2). Medical complications requiring immediate attention: bradycardia, prolonged QTc, orthostatic hypotension, amenorrhea, refeeding syndrome risk (low phosphorus). Treatment priorities: (1) Medical stabilization (inpatient if HR <50, QTc >500ms, or electrolyte instability). (2) Nutritional rehabilitation (supervised refeeding with phosphorus monitoring for refeeding syndrome). (3) Evidence-based psychotherapy once medically stable (FBT for adolescents is first-line). (4) No immediate initiation of weight restoration at high speed (refeeding syndrome risk).
Teaching Points
- DSM-5-TR removed the amenorrhea requirement that was in DSM-IV. Anorexia nervosa can now be diagnosed in males, pre-menarchal females, postmenopausal women, and women on hormonal contraception — groups that were previously excluded if amenorrhea was required.
- Refeeding syndrome is a life-threatening complication of nutritional rehabilitation in severely malnourished patients. It occurs when rapid carbohydrate reintroduction drives insulin secretion, which shifts phosphorus, potassium, and magnesium intracellularly, causing dangerous extracellular depletion. Ms. D's already-low phosphorus makes her HIGH risk. Supervised, gradual refeeding with electrolyte monitoring is mandatory.
- Cardiac complications are the leading cause of death in anorexia nervosa. Bradycardia, QTc prolongation, and electrolyte abnormalities create arrhythmia risk. ECG monitoring is standard of care. Any QTc >500ms or HR <40 warrants inpatient medical admission.
- Family-Based Treatment (FBT/Maudsley approach) is the evidence-based first-line treatment for adolescents with anorexia nervosa. It externalizes the eating disorder as separate from the patient and empowers parents to take temporary control of nutrition. This approach has the strongest evidence base for adolescent AN.
- Poor insight is the hallmark of anorexia nervosa (Criterion C). Ms. D genuinely does not perceive herself as underweight at BMI 15.2. This is not 'denial' in the colloquial sense — it reflects a genuine perceptual disturbance in body image. Treatment must address this cognitive distortion while simultaneously managing the medical crisis.