A 20-year-old woman presents with parotid gland hypertrophy, dental enamel erosion (perimylolysis), calluses on her knuckles (Russell's sign), and normal BMI. She is diagnosed with Bulimia Nervosa. Which electrolyte abnormality is most characteristic?
- A Hyperkalemia with normal chloride
- B Hypokalemic, hypochloremic metabolic alkalosis ✓
- C Hyponatremia with low serum osmolality
- D Hyperphosphatemia with low calcium
Correct answer: B. Hypokalemic, hypochloremic metabolic alkalosis
Explanation
Repeated self-induced vomiting in Bulimia Nervosa causes loss of hydrochloric acid (HCl) from the stomach, resulting in hypokalemic hypochloremic metabolic alkalosis. Vomiting depletes H+ and Cl- ions; the kidney compensates by retaining Na+ in exchange for K+, worsening hypokalemia. Elevated serum amylase (salivary isoform) from parotid swelling, dental erosions from acid reflux, and calluses from manual purging (Russell's sign) are clinical markers. Normal BMI distinguishes bulimia from anorexia nervosa. Hypokalemia can cause fatal cardiac arrhythmias.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.